The lockers across from the desk just past the turnstiles, they say Day Lockers. Do they cost money to use or is it like the lockers in the change room that you just have to bring a lock to use?.

if it says day lockers, just put your lock on one if they are free. if you leave it overnight they will cut your lock

Yep, just put a lock on there and you're good to go for the day. Those ones are a lot smaller than the ones in the change rooms though...