Do you see my signature? Click on each of the green titles, and follow them without skipping any of the steps. (Don’t worry about which version of BitComet there were originally written for - the basics are pretty much the same for all versions.)
Afterwards, if you still have any doubts/concerns, start a new topic (in the proper forum, please) and make sure that you include the Essential information requested. Also, please include as much detailed information (speed test results, settings used, etc.) as possible - too much is preferred to not enough.