Small business: Where can I learn to fix computer beside of school

What do you mean by "fix?"

Do you want to open the computers and resolder connections, or do you want to know how to format hard drives, install new operating systems, automate backups, and other tasks that involve using a mouse and keyboard instead of a screwdriver and needle-nose pliers? I do a bit of both. I think the best recommendation is build your own PC, first. Check out places like Newegg or your local electronics store fore the components. You will find a ton of online tutorials, both video and written, if you search for how to build a PC.

After that, an apprenticeship is a good idea. If the local computer store doesn't go for that, maybe you can ask if you can just hang out and watch for a while. If you're nice and don't get in the way, they may let you. I know you said besides school, but our local Adult Education School offers night and weekend computer classes that cover operating system basics as well as hardware. Might be worth looking into if you just don't want a full semester course.

Good luck!