Acclimating 6 week old chicks

[PotatoChick]

I have some 6 week old chicks and currently they seem fully feathered and are very soft. Currently, I have them in a room that has no heat and is at 65 degrees Fahrenheit. I live in Wisconsin so it's down to 20 right now outside. I have a run and coop up, with plastic covering all sides with draft areas along with a small plate heater inside the coop itself. At most its been around 25 degrees inside it but we haven't hit the lowest of winter yet.
I know it'd be best to slowly acclimate them to the temp but I don't know how I can to make them most comfortable.

 

[rosemarythyme]

Since there's a heat plate inside the coop for them to use if they want it I'd put them in the coop for increasing periods of time for a week, then they should be good to go.