The key to Aluminum welding of any kind is clean, Clean, CLEAN! Physically clean use a stainless steel brush pushing from cleanest to dirtiest, ( best to use a thin diameter bristle stainless steel brush for an angle grinder), then apply an aluminum joint cleaner.
If you have or are purchasing a TIG set up for you welder, the actual welding is pretty simple and straight forward. Notice I didn't say easy. The two main points are; 1. As stated above keep it CLEAN! 2. Keep your tungsten from touching the work piece. It's also a good idea, if you're new to TIG, to keep a sanding wheel on a drill or grinder close. If by chance your tungsten touches the work piece. just use the sanding wheel to make anew point on it.
And as with all endeavors practice maks perfect. Try you skill on a scrap piece first.