Open Roblox Studio
Create or choose a clothing template
Download the official shirt or pants template
Open the template in an image editor
Design the clothing on the template
Save the finished image as a PNG
Go to the Roblox Creator Dashboard
Open the Creations section
Select the clothing upload option
Upload the PNG file
Enter a name for the clothing item
Pay the required upload fee if needed
Submit the item for review
Wait for approval
Use the approved clothing on your avatar or sell it in the marketplace