Am I suppose to convert the file to mp3 first then upload the file to the site?
Yes.
what's happening is, it just gets stuck at upload..
Before you said you were getting an error message that the file was too big?
I'd have expected some timeout message if it didn't work - but I don't know how you are connecting to the internet, what bandwidth you have etc.
Typical internet connections, even broadband ones, are usually slower at uploading than downloading. If the file is several mb, it might appear to be "stuck" simply because it'll take several minutes to upload.
For example, 12mb on a 256kbps upstream speed could take over 6 minutes. So if the file is 1/2 that size 1/2ve the time and so on - if your upstream connection is 1/2 that speed double the time and so on. That should give you a ballpark figure of how long to wait before deciding it's "stuck" rather than just uploading.
HOW DO YOU RE-ENCODE THE MP3 INTO SMALLER BIT RATE? I HAVE SONAR LE (CAKEWALK) SOFTWARE?
I thought teenagers were all computer whizz-kids?

The easiest way, use the original wav and encode that, the same way as you did before, only choose different settings.
But, it's difficult to answer the question because it's not clear yet what you've done that is "wrong", if anything at all.
e.g Common mistakes : some people save a file that's a wav as "something.mp3" and think that's now an mp3, or they try to upload "something.wav" or they try to upload 30 minutes of mp3, or they try to upload an mp3 encoded at a higher-than-is-worth-it bit rate. All of which point to different solutions.
OTOH, if the file you've been uploading is an mp3 and it is less than 12mb in size, perhaps you just weren't patient enough to let it upload as I described above.
If you encoded at 128kbps or less, I'd suggest cutting up the file into sections / movements / pieces, whatever makes the most sense, like others do.
If you're still stuck, record a small section [or take a small section from your existing wav] 30 seconds or less, encode that in the same way and upload it - if that works, we can see what you've done without having to type "you could do this or this or that or if such and such is the case then try this..."
You'll find stuff about encoding to mp3 etc from google probably for the specific software you've got.