Start with the right checks.
Restoring should begin with a clear description of what is missing and when it last existed. That makes it easier to choose the right backup and avoid overwriting newer work.
What to do next.
Identify the backup destination and the approximate date of the needed information.
Check that you can access the backup without modifying or deleting it.
For a user account recovery, open Applications > Utilities > Migration Assistant on the destination Mac, or use it during initial setup. Choose the option for a Mac, Time Machine or startup disk, then select the intended backup. If the Mac cannot start, get help with the recovery route first.
Review the accounts and categories selected before starting. Ask for guidance if the destination already contains important newer information.
Check the result.
Open restored documents and test the applications that use them. Keep the backup available until the intended recovery is checked.
Stop and get help if…
The backup is unreadable, account ownership is uncertain or the restoration would replace newer work. Recovery is not complete simply because a progress bar reaches the end.