In grammar, person refers to the point of view represented by a statement and determines which pronoun to use.

In general, use second person

In second person, you write as though you're speaking to the reader. Second person often uses the personal pronoun you, but sometimes the word you is implied. It supports a friendly, human tone and helps avoid passive voice by focusing the discussion on the reader. Consider omitting you can whenever the sentence works without it.
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Use first person sparingly

Use first person (usually I or me) only when you need to write from the point of view of the customer.
Alert me when a new Bluetooth device tries to connect to my computer. (check box text)

Exception Cortana is a persona, so the use of I is appropriate.

Avoid first-person plural

First-person plural, which often uses the pronoun we, can feel like a daunting corporate presence—the opposite of Microsoft's modern voice. It's OK to use phrasing like we recommend if it helps you avoid awkward phrasing like it's recommended, but write around it if you can. Try to keep the focus on the customer, not Microsoft.
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The scheduled default setting is the easiest way to keep your computer up to date. (Instead of We recommend that you use the scheduled default setting ....)

See also Microsoft