Note: use Mozilla Firefox or Chrome only to install the signature.
Step 1. As soon as your signature is ready, click Save and Install in order to start installation.
Step 2. Choose Install with Google option (as you see on the picture).
Step 3. Choose the account where you want to see your signature.
Step 4. Allow NEWOLDSTAMP to manage the singnatures in your account and enjoy using the product!
Here is the pop-up you will see when everything is set up.
Step 5. Open Gmail, compose a new email and if you do not see the signature or it is not updated, you need to refresh Gmail tab.