Dark Souls Remastered | Knight Lautrec of Carim first encounter full dialogue

If you want his rewards, then after freeing him, you must speak with him at Firelink Shrine. He will then give you a Sunlight Medal and you will see his summon sign near the fog doors of the Bell Gargoyles and the Gaping Dragon boss fights, where you can summon him to help fight the bosses.

Note that freeing him isn't enough to see his summon signs. You have to go back to Firelink Shrine and talk with him first.

You can read more about him here:
https://darksouls.fandom.com/wiki/Knight_Lautrec_of_Carim