Physically, baby chicks are able to navigate vertical challenges after they're one week old and have enough wing development to achieve "lift". So being able to navigate a ramp is the least of your problems.
Motivation is the main issue. It's not always easy to convince chicks to go into a coop at night because they're deeply suspicious of anything unfamiliar.
You can handle this in either of two ways. Wait days or weeks until they get familiar with the set up and decide to do it on their own. Or you can teach them. I opt for the second approach.
I use a favorite treat and get inside the coop myself and lure them inside. In just a few days, they're doing it on their own. It also helps to have a light, temporarily, inside the coop during this learning process.
Now, getting them to roost is whole other ball of wax. I'm still working with my four eight-week olds on that one.