Step 1:
Once you are ready to set up your email signature, open Polymail. In the top menu, click on Polymail and then select Preferences.
Step 2:
On the left-hand menu, select Accounts. In the middle section, select your account and then paste your email signature into the text area under the Signature heading on the right.
Step 3:
Close the preferences window. Your new email signature is now installed! Test it out by composing a new email to make sure it looks correct.