what he actually did by blood bond . bite him or sth?

He gave him his blood. There was panel where he bit his lips and kissed him, marking him in his own way

Tristian swallowed a drop of Ethan's blood. It was in the previous chapter 36. When they were having sex, Ethan bit his tongue with his fang and when Tristian and Ethan were kissing Tristian ended up swallowing a drop of Ethan's blood unbeknown to him.