01-3, entitled slides, is the fourth level in Episode 01, the ninth level in the 00 column, and the ninth level overall.
When you start the level, you will be right under a thwump, so get out of the way, jump on it, and let it carry you to the top. Jump to the second opening and hold the left arrow key so you don't go at full speed. Jump towards the switch, land on the slide, and let it carry you down. Now go back to the left and jump into the other slide. Jump up the slope and get the switch. Go back down, use the thwump to carry you up again, and quickly go across the gaps to reach the door switch. Fall into the first opening you come to, and move to the exit.
Method Three (NEHS)
There is a thwump at the very beginning of the level. Use the "thwump riding" technique you learned in Episode 0 Level 2, and get to the top of the level. Slide down the first two slides, remembering to time your jumps accurately. If you hold the left arrow key down, you can actually jump back up the slide instead of wasting time riding the thwump again. Get to the terminal, then activate it.
On the way to the exit, you'll find the very first gauss turret of the game. These enemies become very common and very irritating in later episodes. This one isn't too bad, just keep sliding and you should be fine.