Hãy đăng nhập, nhập mã PIN rồi quét biểu mẫu.

Hãy is often used to make an instruction or command sound more like a polite directive: please / do ...

In this sentence, Hãy đăng nhập... means something like Please log in... or Log in...

A few useful points:

• Hãy is common in written instructions, manuals, app interfaces, and formal guidance.
• In everyday speech, people often leave it out and just say the verb:
  • Đăng nhập, nhập mã PIN rồi quét biểu mẫu.
• It is not exactly the same as English please, but it often has that kind of function.

They are different verbs with different meanings.

• đăng nhập = to log in / sign in
• nhập = to enter / type in

So:

• đăng nhập is a fixed expression used for accessing an account or system.
• nhập mã PIN means enter the PIN code

Even though both contain nhập, the full phrase đăng nhập has its own meaning and should usually be learned as one unit.

For learners, it is best to treat đăng nhập as a set phrase meaning to log in.

It is made of:

• đăng = register / post / sign up, depending on context
• nhập = enter

But in modern Vietnamese, đăng nhập functions as a standard compound verb for log in. In most situations, you should not try to interpret it word-by-word.

Related expression:

• đăng xuất = log out

In this sentence, rồi links actions in sequence and means something like:

• then
• and then
• after that

So:

• đăng nhập, nhập mã PIN rồi quét biểu mẫu = log in, enter the PIN, then scan the form

Here rồi shows the next step after nhập mã PIN.

Important: rồi has more than one use in Vietnamese. In other contexts, it can also mean already. But in this sentence, it is clearly the sequencing word then.

Because rồi emphasizes order.

• và = and
• rồi = then / and then

This sentence is giving step-by-step instructions, so rồi is better because it shows that one action happens after another.

Compare:

• nhập mã PIN và quét biểu mẫu = enter the PIN and scan the form
  
  • just connects two actions
• nhập mã PIN rồi quét biểu mẫu = enter the PIN, then scan the form
  
  • clearly gives a sequence

Vietnamese often leaves out the subject when it is obvious from context.

In instructions, commands, and interface text, the subject is usually understood to be you. So Vietnamese does not need to say it.

For example:

• Hãy đăng nhập... = Please log in...
• Literally, there is no spoken you, but it is understood.

This is very normal in Vietnamese, especially in:

• instructions
• recipes
• notices
• app and website prompts

Yes, from a strict English logic point of view, it is a bit redundant, just like English speakers often say PIN number.

In Vietnamese:

• mã = code
• mã PIN = PIN code / PIN

This is very natural and common usage. Learners should not worry about the redundancy. Vietnamese often uses mã with many kinds of codes:

• mã số = number code / ID number
• mã xác nhận = verification code
• mã QR = QR code

So nhập mã PIN is perfectly normal.

Yes, quét can literally mean to sweep, but in modern usage it also commonly means to scan, especially with technology.

So depending on context, quét can mean:

• sweep the floor
• scan a QR code
• scan a document
• scan a form

In this sentence, because the context is logging in and entering a PIN, quét biểu mẫu is clearly the technological meaning: scan the form.

Biểu mẫu usually means form, especially an official, printed, or digital form/template.

It is a fairly formal word and is common in:

• administration
• business
• online systems
• documents

Depending on context, Vietnamese might also use:

• mẫu đơn = application form
• phiếu = slip / form / ticket
• form = borrowed from English in casual or tech contexts

So quét biểu mẫu sounds like scan the form in a formal or system-related context.

The comma helps show the steps clearly:

• Hãy đăng nhập, nhập mã PIN rồi quét biểu mẫu.

It separates the first action from the next part of the instruction. Vietnamese punctuation in instructions is somewhat flexible, so you may also see similar commands written with fewer commas, especially in interface text.

The meaning does not change much. The punctuation mainly helps readability.

Yes. The given sentence is natural, especially for written instructions, but everyday spoken Vietnamese might be a little simpler.

Possible versions:

• Đăng nhập, nhập mã PIN rồi quét biểu mẫu.
• Bạn hãy đăng nhập, nhập mã PIN rồi quét biểu mẫu.
• Đăng nhập xong thì nhập mã PIN rồi quét biểu mẫu.

Differences:

• Without hãy, it feels more direct.
• Adding bạn makes the subject explicit.
• xong thì emphasizes after finishing that, then...

The original sentence is still perfectly good, especially for formal instructions or app guidance.