Welcome to the quail forums!
Quail are unlike chickens in that they go into a coop at night and really prefer to sleep outside, if they have such an enclosure. However, that does not mean that they should not be run into their coop should the weather warrants it.
The first thing you should do is lock them in this coop for a couple of days, (as long as it has light and windows with ventilation) so that they become familiar with it and are not afraid to use it. They will then find comfort in being in there and may go in on their own if the weather turns bad.
However, still there may be days that they do not want to go inside and you want them to go inside. You need to train them to get inside should there be an emergency, you need to clean or as you have suggested here, go inside at night on cold nights.
I keep my birds in an aviary and their coop is an elevated one as well. I clicker trained them to get in the coop so that I can get all of them in without having to physically handle any of them.
Once your birds have been in this coop for a while and feel comfortable using it, you can work with them on getting them in. What I did was get my handy dandy quail net and a dog clicker. I did not chase them around with the net, but showed them the net and clicked the clicker, all the while telling them to "get into the coop". (you may need to block off the underneath so that they have no choice but to run from the net and up the ramp, or get caught in the net.) They had no other place to go but into the coop or be snagged by this net. At least that is what they thought. Quail are pretty smart and learn pretty quick. I rewarded them with a tray of meal worms so that they relaxed once they got in. Over time, they no longer needed the net, or the treat, just the click of the clicker and sometimes just telling them to "get into the coop" will get them started.
Work with them, come up with your own training means. It can be done. Good luck!
