Images Won't Upload

I designed my site on my desktop using MAMP.

Then I uploaded the site, and also I uploaded a new database sql file to my web server through the hosting company.

The site works just fine, however, I cannot upload images, period.

I’m not good enough with this kind of thing to figure out where the problem is. I’m assuming it is in that new database file I uploaded.

Any suggestions on how I can easily remedy this? (Keeping in mind I barely figured out how to do what I have done so far!)

Thank you in advance!!!