You need to click on the arrow blocks and use them to push the dot to the finish line.
There's two parts to this puzzle:
1. Get the dot to the top
2. Get the dot over to the door
Which part are you stuck at?
The arrows can push each other. So you can use this to get an arrow that "moves only right" to the left of the dot.
Or you can bypass all of that with the unintended solution shown in this guide: Steam Community::20 Small Mazes