Baby doesn’t understand bottle

My son is seven months old and has been EBF his entire life.

I’m trying to get him to drink some prune juice per the doctor’s suggestion because he hasn’t had a BM in over a week 😳

Unfortunately, we haven’t had much practice with a bottle and he just can’t figure it out. When I Google the issue, it only gives me tips on babies refusing the bottle. He’s not refusing it, he’s just chewing on it instead of actually locking on and drinking.

Did anyone else have this issue? How did you resolve it? Just keep practicing and hope he figures it out? Lol