In the past, Redgate products could be activated using just a serial number. In order to make it easier for you to manage your licenses and know who’s using a product, activation in most of Redgate's desktop products now also requires users to log in with their Redgate ID.
Download and install the product. On the first run after installation, you are prompted to log in with your Redgate ID to activate the license. If you don't have a Redgate ID you can follow the links in the client dialog to create one.
You are only required to log in with your Redgate ID once on each computer, either through installing a product for the first time or updating an existing product. As other products are upgraded or installed on that computer, they'll be activated using the same Redgate ID.
Logging in with the same Redgate ID each time will only consume one entitlement. If an additional Redgate ID is used, this will consume another entitlement.
If you are getting the message that you have run out of entitlements, you probably haven't logged in; on the toolbar of the tool, click on Help>Manage license and you'll see here if you're logged in: