Step one. Go to a tree and chop it down.
Step two. Go to your workbench and craft a wooden stair.
Step three. Craft 2 signs.
Step four. Put the signs on each side of the stairs.
Step five. Now in the right angle you can crouch, press f5 and now it will look like you have a chair!

(Optional) Also put two stairs next to each other and do the same instructions and you have a couch!

This is a broadcast from Ploopy's simple tuts!