Inside Roblox Studio, you can create new games by clicking + New tab on the left hand bar. This will bring up a series of templates for you to work from that can be sorted by theme or gameplay style.

How to get a Roblox character to build from Although you can create a character from scratch, it isn't easy to do if you’re new to Roblox Studio.

Much like most things on Roblox, you will be making this yourself from scratch, so you'll need to design a t-shirt in an image and then upload it to Roblox.