a weep hole is for when water gets on the sill and it is allowed to "drain". This only applies to vinyl windows. Ususally found on the sides and can either be a slit or a drilled 3/8. DO NOT USE THE PREDRILLED 3/8. That will void the warranty. Then there are little slits in bottom outside of windows for water to "weep".
Why pop off the molding, just get some 3-4' divesibits to drill right down through the bottom plate into basement.
Like that idea bigpapa about drilling 3/4 top and 3/8 low in channel. Have always just done 3/8 3/8 and put tons of silicone in there. So far have never had to go back and service tho. bet its no fun pulling them out after the fact.