you cool the plastic bead as soon after laying it on top of the last layer as you can.

You need the bead hot and sticky so that layers bond well, but you also need to then cool it to set it in the right shape.

If you look on thingiverse you should find cooling duct designs for most printers
here's one: https://www.thingiverse.com/thing:1738499
There is a huge folgertech collection on thingeiverse :-)