The way it works is super simple. Call them, and set up an appointment at your house. Both/either of them brings samples of the chicks they have- they've got a collection of about 60-70 chicks in all colours that you can choose from (customisation isn't possible from what I remember.) They measure the space/frame, you deposit an advance, and within a week tops your chicks are installed and up!
What I like about them is how earnest they are, and that they get the job done on time (unlike most other contractors etc I've dealt with). The quality of the chicks is fabulous! Super sturdy!
If you're looking for a chickwaala whose work is ace, give Mr Thapa a call. They're pricier than the roadside chickwaalas, but their quality is excellent.