Navigate to the Signatures tab and click the “New User” button.
When clicking the "New User" button, you will be prompted to enter a display name and email address for the new user. Don’t worry, these details won't be used for the signature itself and you can change these settings later.
You will also be asked to place the new user into a group, so you can either create a new group or select from one of your existing groups.
Remember, if you have previously applied fields at the group level, this will apply to all new users that are placed into that group too. For example, if you have applied the “Company” field to the group, that field will apply to the new user.