tayousoninsyou de ninsyoukoodo wo tukau.

A natural breakdown is:

• 多要素認証 = multi-factor authentication
• で = in / with / using / for
• 認証コード = authentication code / verification code
• を = marks the direct object
• 使う = to use

So the structure is basically:

• [in/for multi-factor authentication] [authentication code] [use]

Japanese often puts the context first and the main action at the end.

Here, で shows the means, situation, or context in which something is done.

So in this sentence, 多要素認証で means something like:

• in multi-factor authentication
• for multi-factor authentication
• when using multi-factor authentication

It does not mean location here in the physical sense. It tells you the setting or method connected to the action 使う.

The particle を marks 認証コード as the thing being used.

• 認証コードを使う = use an authentication code

This is a very common pattern:

• X を 使う = use X

Examples:

• スマホを使う = use a smartphone
• アプリを使う = use an app
• 認証コードを使う = use an authentication code

Because 認証 means authentication/verification, and both words are built around that idea.

• 多要素認証

  • 多 = many / multiple
  • 要素 = elements / factors
  • 認証 = authentication
    → multi-factor authentication

• 認証コード

  • 認証 = authentication
  • コード = code
    → authentication code

This kind of repetition is very normal in Japanese technical language.

The usual readings are:

• 多要素認証 = たようそにんしょう
• 認証コード = にんしょうコード
• 使う = つかう

So the full sentence is read:

• たようそにんしょう で にんしょうコード を つかう。

Because Japanese normally uses Subject/Object/Verb word order, and the verb usually comes at the end of the sentence.

In English, you say:

• Use an authentication code in multi-factor authentication.

In Japanese, the action word 使う comes last:

• 多要素認証で 認証コードを 使う。

This is one of the biggest structural differences between English and Japanese.

Yes, the subject is omitted.

Japanese often leaves out subjects when they are obvious from context. This sentence could mean things like:

• You use an authentication code in multi-factor authentication.
• We use an authentication code for multi-factor authentication.
• An authentication code is used in multi-factor authentication.
  depending on context

A standalone Japanese sentence often sounds less explicit than English.

使う is the plain dictionary form.

That form is commonly used in:

• headings
• instructions
• explanatory materials
• notes
• casual writing

If you wanted to make it polite, you could say:

• 多要素認証で認証コードを使います。

That would sound more like a normal polite statement.

Usually で is the better choice here.

• で fits because it gives the context/method/situation for using the code.
• に would not sound natural in the same way here.

So:

• 多要素認証で認証コードを使う。 = natural

Using に here would likely sound wrong or force a different meaning.

It is grammatically complete, but it can sound a bit like a manual, note, or UI instruction rather than a full conversational sentence.

In technical or interface language, this is very normal.

More conversational full sentences might be:

• 多要素認証では、認証コードを使います。
• 多要素認証で認証コードを使用します。

The original sentence is short and efficient, which is common in technical contexts.

Both can mean to use, but the tone is different.

• 使う = ordinary, common verb
• 使用する = more formal, technical, official

So:

• 認証コードを使う = everyday/plain
• 認証コードを使用する = more formal/technical

In manuals, security settings, or business writing, 使用する is also very common.

Japanese normally does not use spaces between words in standard writing.

So the usual written form would be:

• 多要素認証で認証コードを使う。

Spaces are often added in learning materials to make the structure easier to see. They are helpful for beginners, but they are not standard in normal Japanese text.