You will have to get it on your own or you can apply for a student license here.
Right now you can only work fully with Maya 2015, Maya 2018 and Maya 2023.
NEW: There is also a tutorial on how to get a Maya trial:
Simply select Maya 2023 at ~02:28
Starting with patch 11.3 Riot stopped using the old .skl format that RiotFileTranslator for Maya exports, so now you will update them every time you make your own remodel or you want to use an old remodel custom skin.
Maya script that detects vertices that have more than 4 influences assigned to them
Download: Maya VertSelect.MEL Script
Align your UV shells from multiple models easily
Download: UV – Helper By Marcius922
Other useful 3d-Tools
3D-Viewer that can play animations – Demo is enough unless you want to extract the models!
Make sure to grab the League of Legends SCO/SCB Plug-In from the third party Plug-Ins, otherwise it won’t load .skn files
.skn Viewer that can also load animations and export posed models, more complicated to use
Original Riot skin viewer, browser, can play all animations
Original Riot skin viewer, phone-app
Turnarounds of League of Legends skins