How do I change my email signature?

Short answer: Open Promotions, tab “Email Signatures”. A first signature has already been built for your organisation: on that one, the logo and the background color can be changed.

The signature already in place

Your account has a signature built automatically from the start: it takes one of your logos, your shop's color, the name of your organisation and the link to the shop. It is marked “Default signature” and offers itself for every new send.

Steps to change it

Open the Promotions page, then the “Email Signatures” tab.
Click the edit icon on the “Default signature” card.
Change the logo with “Choose an image”, and the shade with “Background color”.
Save.

On that particular signature, the organisation name and the shop link cannot be typed into: they carry the note “Automatic value, locked on the default signature”. That is deliberate — they follow your account, so renaming the organisation updates the signature by itself.

Creating another signature

Click “New Email Signature”, then choose:

“Create with the standard template” — the same form as the default signature, but with the name and link editable;
“Start from blank” — a free editor, where you compose whatever you want.

The “Default signature” switch marks the one that will be offered automatically; there is only ever one at a time.

Cards can be reordered by dragging them. The default signature stays at the top and does not move.

What cannot be deleted

“The default signature can't be deleted, and every account must keep at least one signature.” The delete icon is inactive in those two cases, and its tooltip says so.

Reusing the signature in Gmail

“Copy for Gmail” puts the signature on the clipboard, formatted. Paste it into the Signature area of your Gmail settings.

Going further

You'll know it worked when: The signature you want appears in the preview on its card, and is offered in the “Signature” field when sending.