In livesplit, go to edit splits, and press autosplit or something like that. It should then split itself
To set up the autosplitter:
Right click livesplit click edit splits > make sure your game is set to portal > Activate the autosplitter > open the autosplitter settings and make sure your game process list includes hl2.exe > close the edit splits window > right click live split > hover over compare against > click game time
If you don't want to use the autosplitter you can do this - fair warning if you don't use the autosplitter comparing against game time, your runs will be placed at the bottom of the leaderboard under all of the runs that do:
Right click live split > click settings > check global hotkeys > uncheck deactivate for other programs > set the hotkeys you want to use
It was recently discovered that it is possible to set your mouse sensitivity to a value so high that the game considers it infinite, leading to several new glitchy techniques being discovered.
The rules have now been amended to ban these new techniques in both Inbounds No SLA Legacy and Glitchless.