If you haven’t noticed, just to the right of the post titles are two little icons.
The first currently looks like “<>”. If you punch it, it will expand the post out (losing the columns on the side) and will turn to “><“. Punch it again and it will collapse to normal.
The second icon looks like “-“. If you click it, it will collapse the current post, bringing the next one up, and turn into a “+”. Hitting it again expands it back to normal.