Uncategorized posts problem, any fix?

HI, I’m new to wordPress and knew some of its difficulties and thought I can easily fix this issue, but I gave up.
I installed a classifieds ads theme, I did everything as mentioned in the tutorial but when i post an ad, it goes into Uncategorized cat, the ad form has the category list and I tried posting ad with all the categories but it still goes Uncategorized, and from admin panel it’s working fine posts go to the desired category. Can anyone please help me out. That issue is really tiring. I know you guys had sorted out that problem on your website