Helicopters with landing skids, no wheels; How are they taken in and out of a hangar?
Basically, you put wheels on the skid and tow them. 

In some cases, towing wheels are attached to the skids (which usually have sleeves in them for mounting), and a tow bar is attached to the front (one or two sets of wheels may be attached to the skids), which is then towed by a vehicle.



Image from incrediblediary.com

There are also specialised tow carts available for helicopters, which basically grip the skids (usually in a couple of places on either side) and lift them up, after which the helicopter can be moved by the operator by controlling the cart.



Image from hasmak.com