Welcome to the CC creator pool. You can either start in the shallows, or dive head-first into the deep-end. I recommend the shallows first. What does this entail? Starting small.
Since you don’t have any prior experience you should get yourself familiar with using blender since that is needed to import meshes into S4S. There are plenty of handy tutorials both on the Sims4Studio forums (so be sure to sing up for an account), as well as YouTube on how to do the basic stuff you should become familiar with. Not everything you need to learn is in the Sims community, a lot of it is outside of it so you will need to brush up on any research skills you have and take to Google to find the answers you need. You should also choose a graphics editing program such as Photoshop, Paint.net, Gimp, or alike to edit and make textures. Again, how to use these are rarely found within the community (except for specifc methods) so be sure to check out YouTube and google on how to use the program you choose.
Take it one step at a time. I never recommend taking on a big project first off. It does work for some people, but generally speaking, most people benefit from starting small. You said you wanted to make maxis match content? Perhaps start by recolouring a rug. This introduces you to the textures first so you become familiar with them and how they work. DDS format that is utilised by the game obeys a certain size rule of 4. Images have to be a certain size to be recognised by the game. Even though you can export as a PNG, S4S still converts that to a DDS for you. Reading up on what size a dds texture needs to be will definitely help in the long run. Once you are comfortable with how textures work and how to recolour them, add a new challenge like a mesh edit which will introduce you to the UV map. Go one setting yourself a goal at a time. Its ok to take it slowly. It has taken me 7 years to get to where i am now.
Hopefully that gets your started on your path to becoming a creator. It wont be easy, but remember: its a lot more fun to do all these things if you actually enjoy it along the way. The community should not put expectations on anyone, so be sure to remember that. Do it for you and the rest will come in time.
