Hi Joseph.
here is the step by step process that I went through to become a stormtrooper.
1. I decided that I wanted to become a stormtrooper after talking with 501st members at a local convention.
2. I joined the FISD as you did to find out what I needed to do.
3. I looked through the link that has been posted above by @gmrhodes13 and started doing research on the various costumes and where to get these costumes. Once I had done that, I ordered my kit from a local armourer.
4. Once I ordered my kit, while I was waiting for it to arrive, I started to watch lots of videos and read threads on how to build the costume to meet the requirements to join the 501st.
5. Once my kit arrived, I created a build thread and started the build process. This is a long process but I made a build thread and the awesome people here at FISD helped guide me along the process through my build thread.
6. Once my kit was finished, I applied for basic approval to the 501st through my local garrison. At this point, I needed to make a few improvements to my armour. Once I fixed the issues, I resubmitted my application and was approved.
7. Your TK number will be assigned to you (picked by you) once you are approved into the 501st Legion. You get to pick your own 5 digit number as long as no one else has it already.
This is a long process and it took me almost 1 year from step 1 to step 7. It may seem daunting but you will find a lot of help here and possibly from your local garrison.
For some people, the building process may be outside of what they are able to do. Some have got their armour built for them by the armourers. This will cost a fair bit more money and you likely will still need to make some adjustments but it is an alternative way to build your kit.
I hope this helps you get started on your journey to becoming a stormtrooper.