First go to the Settings from there click on File transfers there you will see at the top right a box that has the file path your using now.
Click the Change box, this will bring up a box so that you can browse for the folder you want to use, and choose highlight it and click OK.
Now you have your incoming folder changed.
Remember its always a good idea to keep your Incoming folder unshared until you can go through your new files, check that they are good and named properly before you share.
This will also keep you from sharing incomplete files. They are not good to share because if you have a rare file and hundreds of ppl download it from you...every ones will be incomplete.