To center your Instagram bio:
Open the Notes app on your phone. Create a new note.
Paste your bio and add spaces to it.
Copy the bio from Notes by selecting all (including spaces)
Open the Instagram app and go to Edit Profile.
In the bio section, paste the text.
The amount of spaces you add to the text will dictate if it gets centered or not. If not, go back to Notes and adjust the spaces as you like.