I don't understand how to run wiiware games from my wii

 

Ok. But how do I run downloaded ones from USB loader or SD card?

 

Wow very clever response. Well done there lad. /sarcasm

 

But on-topic: to play your wiiware from USB or SD, you need to look into nand emulation. There are three ways to do that:
1. sneek. this is rather complex, and if you're new to hacking, you best try one of the other methods first.
2. triiforce. this nifty program (or it's graphical mod "triiforce_mrc") is a bit easier. It's the most popular choice around here, and there's a decent "how to" guide in the complete softmod guide (check the "modify any wii 4.2 and below" thread). After setting up the emulated nand, you can install your wads to it by using showmiiwads. Once this is done, it's all a matter of running triiforce.
(note: triiforce doesn't work on Waninkoko's rev18 or 19...it's best to install 17 to get it to work)
3. uloader. this is a relatively new feature of this loader (from version 5 onward, iirc). It requires v5 of Hermes's cIOS, but once that is installed, it's pretty straightforward: just put the .wad's in the correct location and run uloader. It'll create an emulated nand automatically and also installs any .wads that are in that location. It's usually still some fiddling which cIOS the wiiware games exactly need, but once you've got it set up, it's all good. (note: for details, check uloader's readme).