Once you are ready to set up your email signature, open the Windows 10 Mail App. From the bottom left menu, click the Settings cog and then click on Signature in the right-hand pane that opens up.
Select your email account or choose “Apply to all accounts” if you want the signature to be installed for all email accounts in your Mail App.
Ensure that “Use an email signature” is switched ON.
In the signature text box, paste (or press CTRL+V) your new or updated email signature.
Once done, click Save.
Create a new email and check out your new signature!