I bought a partly dissembled bike at a discount price because I'm a university student, and I wanted an easier way of transport than walking. It's an Expert EXPMTB18SPD31. I've hit a wall, though- the only parts of the bike that came pre-assembled were the chain, the back wheel, and the braking system. I put the front wheel, but I didn't realize it until after that the brakes are positioned behind the bar. Also, when I squeeze the front brake on the handlebar, the brakes close a little but do not stop the wheel. I'm not word-savy, nor am I a mechanic, so any advice would be really appreciated. Thanks in advance
First, please do not ride the bike in it's current condition with the fork reversed or the front brake not functioning, it is dangerous. The steering will be unstable and you may not be able to stop quickly enough.
You have two things to do:
1) Un-reversing the fork, obviously.
2) Adjusting the front brake (and checking the rear brake).
To un-reverse the fork/handlebars. The 'quill' style stem must be loosened. Loosen the hex bolt in the top of the stem (you don't have to undo it all the way), the bars and stem will come loose from the fork steerer tube in the headtube, rotate the forks 180 degrees, replace the stem, align the bars and tighten the stem.
A couple of things to be aware of:
Make sure the stem is tight, you do not want the bars and forks coming apart when you are riding.
Make sure the stem is inserted into the fork steerer tube far enough. There may be a 'minimum insertion' mark on it. In your picture it looks like it may not be inserted far enough.
If you need additional help, there are many bike maintenance videos and articles you can search for. Just Google for 'bicycle quill stem adjustment'.
The front brake cable as shown in your picture is far too loose. Brake adjustment is too complicated for me to describe here so I recommend watching the Park Tool video on linear brake adjustment. Park Tool bike maintenance videos are generally well thought out and accessible.
You should check the rear brake adjustment when you address the front brake, to verify it is working properly.