You have two options for adding a signature:
Option 1: Add the signature directly to your email account in the Email Accounts page.
This is a fixed signature and does not support spintax.
Option 2: If you want to use spintax or dynamic variables, build the signature directly into your sequence.
You can include custom variables like {SENDER_FIRST_NAME}
or {SENDER_FULL_NAME}
to personalize each email.