Click the gear icon
Click Setup
Search "Data Import Wizard"
Click Data Import Wizard
Click "Launch Wizard!"
Under "What kind of data are you importing?", Click "Custom Objects"
Scroll to and Click "Products"
Click "Add new records"
Drag & Drop CSV file or Click CSV button
Click Next
Map any relevant unmapped fields
Click Next
If everything looks like the image below, click Start Import
Click OK