Open Roblox Studio
Create or choose a clothing template
Use an image editor to design the clothing
Make sure the design matches the Roblox template size
Save the design as a PNG file
Go to the Roblox website
Open the Create section
Upload the clothing image
Pay the required upload fee if needed
Wait for Roblox to approve the item
Test the clothing on an avatar
Adjust the design if needed
Reupload the updated version
Publish the clothing for others to use