Go to PLAY MODES, CAREER MODE and PLAY AS MANAGER (you can pick anyone, I just chose Pep from Manchester City so I knew I had a lot of money) and make sure the TRANSFER WINDOW is ENABLED when creating. Once created and in the hub, navigate to the TRANSFERS tab and click TRANSFER HUB, push in the RIGHT STICK
to SEARCH PLAYERS and change the TRANSFER STATUS to FREE AGENTS. Click on any of the players, followed by SHORTLIST AND VIEW IN TRANSFER HUB. Once in the hub simply click SHOW ACTIONS, then APPROACH TO SIGN and offer some crazy amount of money to sign the player. I did Important Role for 3 Years with No Release Clause, but for those I don't think it matters too much, just ensure they are happy and want to sign. I tried this on a few free agents and it always resulted in an A rating. After the signing has been completed you will get your rating.
I created this video to help:
Hope this helps.