Omg I figured it out finally! I was able to do it on the EA Racenet app on iPhone, so it may be different if you try it on something else.
Step 1) Open Racenet app and go to your league (the exact location of your photo)
Step 2) Press the Red/Orange “MANAGE LEAGUE” button
Step 3) You should have four options to click on. Press the bottom one “Seasons”
Step 4) You should have three options to click on. Press the top one “EDIT SEASON SETTINGS”. It should be smaller than the other two boxes and in that same Red/Orange color as Step 2.
From there you should be able to edit all of those settings! Just make sure you press Save at the bottom when you’re done.