Sessions are located in the Leagues - League Sessions tab, here you see sessions of all leagues in which you can take part.
You can also go to the Leagues - My Leagues, select TIERacing and register in the session in the Sessions tab. When it starts, of course.
REGISTER YOUR TEAM CORRECTLY!
First, select the desired team (or create one in the My Teams tab), then select the drivers who will participate, and only then click Register Team. If you register a team drivers roster cannot be changed!
Next, register as a driver. The second driver only needs to register as a driver in the same tab or in the My Teams tab, your team - Sessions and register here.