Chiharu Ochl

hi guys, so I´m a rl fashion designer and my rl husband is a photographer. We have a decent life but friends are encouraging us to start a SL cloth store. Sounds good to us, problem is we have no idea how to start. lol We aren´t much of 3D modelers, but for example to start things with something simple: T-Shirts. I guess there may be something like a universal shirt template you can edit in Photoshop to add your own textures. But how do you import them to SL as a wearable shirt? What software do we need and how do we get it? TY