Signatures
Manage the team's signatures from Settings.
Settings > Signatures lists every signature, split into a Shared tab and a Private tab: shared signatures are set by an administrator, private ones are yours alone.

Go to Settings > Signatures.
Select New signature.
Enter a name to find it by later.
Choose whether it's shared or private.
Under Channel access, choose which connected mailboxes it applies to, or leave it as all channels.
Write the signature body.
Select Save.
A signature is added automatically to a new email from a mailbox it applies to. Remove or edit it in the composer for any one message without changing the saved signature.