Help with tropical fish RE Bloodworm feeding?

Does anyone know about feeding with Bloodworms (frozen)? I was suggested
this at the petstore, bought some, but I'm a little lost on the best way to
go it. He said to put some into a small cup and add water. Is there a
recommended amount? My 20 gallon has 8 fish ranging from 1-2.5 inches. I
tried a little bit this afternoon and they did not seem to respond too well,
I'm afraid continuously doing this might pollute the tank.

He also suggested these for my male Beta and again, not sure on the amount.

Should I be putting them in water FIRST or adding the fozen ones straight to
the tank? I cant seem to find any feeding directions online.

Thanks all