Ontem cliquei no ícone errado e esqueci-me de anexar o documento ao e-mail.

Ontem is a standalone adverb meaning yesterday. In Portuguese, you normally use it by itself, without a preposition or article.

• Ontem cliquei... = Yesterday I clicked...

This is different from expressions like:

• na segunda-feira = on Monday
• de manhã = in the morning

So ontem works more like the English word yesterday: no extra word is needed before it.

Cliquei is the 1st person singular form of the verb clicar in the pretérito perfeito (simple past / preterite).

• clicar = to click
• eu cliquei = I clicked

This tense is used for a completed action in the past, which fits well with ontem.

A few forms of clicar:

• eu cliquei = I clicked
• tu clicaste = you clicked
• ele/ela clicou = he/she clicked
• nós clicámos = we clicked

The sentence describes two finished actions in the past:

• cliquei
• esqueci-me

No is a contraction of em + o.

• em o → no

With clicar, Portuguese often uses the preposition em:

• clicar em algo = to click on something

So:

• cliquei no ícone = I clicked on the icon

More examples:

• Cliquei no botão. = I clicked on the button.
• Cliquei na ligação. = I clicked on the link.

Here:

• o ícone = the icon
• em + o ícone = no ícone

In Portuguese, adjectives often come after the noun, especially when they describe something in a straightforward, literal way.

• o ícone errado = the wrong icon
• o documento importante = the important document

So errado follows ícone in the normal order.

Sometimes adjective position can change meaning or emphasis, but here ícone errado is the natural choice.

This is a very common feature of European Portuguese. The verb here is esquecer-se de, which is a pronominal/reflexive-style verb.

• esquecer-se de algo / de fazer algo = to forget something / to forget to do something

In affirmative main clauses, European Portuguese usually places object pronouns after the verb, joined with a hyphen:

• esqueci-me = I forgot
• lembrei-me = I remembered
• chamo-me = my name is / I am called

So:

• esqueci-me de anexar... = I forgot to attach...

This is one of the big differences between European and Brazilian Portuguese. In Brazil, you will often hear me esqueci, but in Portugal esqueci-me is the standard pattern here.

In European Portuguese, the more standard and expected form is:

• esqueci-me de anexar

That is because the usual verb pattern is esquecer-se de.

You may sometimes come across esquecer de without -se, especially in less formal usage or in other varieties of Portuguese, but for Portugal, learners should strongly prefer:

• esquecer-se de + infinitive

Examples:

• Esqueci-me de ligar. = I forgot to call.
• Esquecemo-nos de pagar. = We forgot to pay.

Because the verb pattern is:

• esquecer-se de + infinitive

So if you forget to do something, Portuguese uses de before the infinitive verb.

• esqueci-me de anexar = I forgot to attach
• esqueci-me de responder = I forgot to reply
• esqueci-me de enviar = I forgot to send

This is just part of the construction you need to learn with esquecer-se.

The verb anexar usually follows this pattern:

• anexar algo a algo
• attach something to something

So:

• o documento = the document
• a o e-mail → ao e-mail = to the email

That gives:

• anexar o documento ao e-mail = attach the document to the email

This is another contraction:

• a + o = ao

Compare:

• anexei o ficheiro ao e-mail = I attached the file to the email
• juntei o documento à mensagem = I attached/added the document to the message

Because the idea is attach X to Y, not put X in Y.

With anexar, Portuguese normally uses a:

• anexar um ficheiro a um e-mail
• attach a file to an email

So:

• ao e-mail = to the email

If you said no e-mail, that would suggest something more like in the email, which does not fit the usual verb pattern with anexar.

E simply means and.

It links the two past actions:

• cliquei no ícone errado
• esqueci-me de anexar o documento ao e-mail

So the sentence is structured very naturally:

• Yesterday I clicked on the wrong icon and forgot to attach the document to the email.

Yes, e-mail is very common and widely understood in Portugal.

You may also see or hear:

• correio eletrónico = email, electronic mail

But in everyday use, e-mail is extremely common, especially in business, technology, and ordinary conversation.

Also, in European Portuguese, you may hear ficheiro instead of arquivo for file, so a very natural Portugal-style sentence could also be:

• Esqueci-me de anexar o ficheiro ao e-mail.

Because the whole sentence describes completed events that happened yesterday.

• cliquei = I clicked
• esqueci-me = I forgot

Both are in the pretérito perfeito, which is the usual tense for finished actions in the past.

If Portuguese used the imperfect here, it would suggest repeated, ongoing, or background actions, which would not fit the meaning as well.

So the past tense in both verbs makes the sequence very clear:

1. You clicked the wrong icon.
2. You forgot to attach the document.

You would need to change only the noun phrase:

• Ontem cliquei no ícone errado e esqueci-me de anexar os documentos ao e-mail.

Why?

• o documento = the document
• os documentos = the documents

The rest of the sentence stays the same because anexar still works the same way:

• anexar algo a algo

So:

• anexar os documentos ao e-mail = attach the documents to the email