is the Enhanced Effect that is on charms a passive skill that extends to melee weps?
or is it only for like wizards and stuff?

Enhanced Effect only helps the item that it is on. side mods on the charm will help melee weapons like critical strike for example.
If enhanced Effect is on a charm then it will make it heal more or do more damage.

ohh ok thx..so I have a barb (first char lol) so what kinda charms should i look for

and what is the acc. charm slot?

It depends on what kind of weapon you're using. You find/allocate stats based on your weapon. http://ladderslasher.d2jsp.org/index.php?g=3
So since you're using clubs, you should find str armors/charms. If you prefer tanking, then go for enhanced effect armors (scales, leathers, chains, plates).

The Accessory Charm is an additional Equipment slot reserved for a second charm. The Accessory slot however does not reflect stats that are on that charm, with exception to Enhanced Effect. Efficiency is reduced by 25% of the total displayed. This charm is used just like the main charm slot and is not reflected by your total inventory space restrictions like the rest of your equipment. When used in Catacombs, the mana usage is also reduced by 25%.
In the inventory, it is abbreviated as Acc. Charm