Cheers,
We don't know yet how the kit format is going to be in PES 2022 (since it is being made on a new game engine it probably will change), so we can't really prepare for it yet. Everything I'm saying down below is valid for PES 2021 and might not be for PES 2022.
If you want kits for PES 2018-2021 there are some places you can check. Many kitmakers are on twitter, so that's a good place to start. But there are also other forums/websites like PesTeam.it, WEPES_Kits subreddit and some youtube channels with good content.
I'll leave here some links I found that could be interesting for you:
https://www.reddit.com/r/WEPES_Kits/comments/k460h7
Each kit in PES is just a image (generally a .png) that follows a certain template. This template hasn't changed since PES 2018 so in PES 2021 you can use any kit from PES 2018 up until PES 2021 (PES 2017 not so much, since the template changed a bit from PES 2017 to PES 2018). With a little image editing knowledge you can even make your own kits
When I started myself I didn't really follow a tutorial or a video, I downloaded a couple templates and started messing around in a program called paint .net, it was kinda of a "learn as I go" thing.
There's also a website where you can create kits - PESMaster. It's a great place to start if you want to do kits on your own
To import kits (into PS4/PS5, PC is similar but not sure how it's done) you just need a USB Flash Drive, create a WEPES folder on it and put all the image files you want to import in there. Then in the edit menu in-game there is an option to import those images.
About making .ted files with images attached, it couldn't be any easier - when you export a team, the .ted file includes not only the data of the players and team details, but also automatically saves the name of the image files you use (logo, kits, etc.) so if you keep the .ted file alongside those image files in your WEPES folder it will all be imported and applied automatically when you import the .ted file. So, all you need to do is put all the images you use next to the .ted file on the WEPES folder (and yes, it can be organized into subfolders, it still works). You can't rename the image files though, if you change the name of a image file it won't import automatically. Remember, this is for PES 2021, for PES 2022 we can't know yet how it will function.
I hope this helps in any way