When logged into your Experticity profile, look for your profile icon in the upper right of the screen (if you have uploaded your photo, this will be your picture).
Click on that, then go to the first option that says "Manage Groups". Click on the Add a Group tab, and from there you'll be able to search for your new retailer and/or group. Once you find them, click on that icon to fill out the application and upload the necessary credentials.
Please apply only to groups or retailers that you work with.