Once you have installed RiftGG, you will have to validate the license assigned to your account. To do so, you have to introduce the mail and password you used to register in our web. You can also do social log-in to do this process so you don't need to register in the web.
Bare in mind that this is not a login process. This process is to validate the license that can be only validated once. RiftGG is a desktop software, so you do not need to log in or be connected to internet to analyze with it.