If your adding the bleach directly to the water, there's no issue at all. Sometimes I like to walk around the pool dribbling it in. Sometimes I just pour it in front of the return.

What you don't want to do is pour bleach in the skimmer IF you are using a automatic chlorinator or put pucks in the skimmer (some people do that).

Otherwise, if you add it to pool directly, you don't have to wait at all.