To learn how to create a signature for every sending account, read this article.
Add a signature using variables
These are special variables that you will have to write down manually in the campaign editor. Variables to use:
Sending account's full name:
{{sendingAccountName}}
Sending account's first name:
{{sendingAccountFirstName}}
Sending account's email address:
{{sendingAccountEmail}}
It essentially takes the value from the sending account's name, whatever value is set in the account's settings section. As the sending email accounts are rotated, their specific settings values are used. Please check the detailed steps here.
Add a signature using an image
Check this article for a step-by-step guide: How to add images
Add a signature using HTML
To add HTML signatures, you will need to click on the Code View and add the HTML code there.
You can use some of the online signature generators to get the HTML code, and then paste it to the Sequence editor's "Code View".