Before starting the below you will want to get a game plan together. Do you want to organize by each sector: Dirt, Street, ATV/UTV, etc.? Or do you want to keep it simple and go Parts and Apparel? There is no "right or wrong way"
Step 1 - Download your existing category structure out of PSS.
To do this go to File Center and Schedule a Job.
Next, select Webstore Categories and Products: Client: Export Category Structure
Step 2 - Retrieve your Category Export File (.csv) from File Center and Open
*You cannot "edit" the categories You must delete existing and create new. If there is a category you want changed you must delete it and create the one you want.
*To delete a category simply put a 1 in the delete column
*To add a category, list it on the csv and make sure it does not have a 1 in the delete column
Step 3 - Upload your revised Category Structure .csv file
From File Center > Schedule a job; Select Webstore Categories and Products: Client: Import Category Structure. Categories should be live on site within an hour.