Last Autumn, Riot announced that League of Legends will be introducing a practice tool. This would place players in a single player environment would allow them to test different characters, tactics, and abilities without wasting time in custom games.
“Our development process for Practice Tool has been slightly different than the way we usually do things with other features. We’ve chosen to target getting a ‘bare-bones version’ of the tool working for you guys as soon as possible (so you can start practicing while Season 7 is still young), rather [than] wait much longer to release something more polished but would still have very similar functionality,” Riot explained.
Riot stated that the tool will upgraded and updated as League of Legends evolves.
The training tool is available under the “Training” tab—update your client if you don’t see it and you should be set.