Carl's advice is correct, but to directly answer your HOW-TO drain a vinyl pool question, there are 2 methods:

1. Hire a vinyl liner installing company to drain it, without destroying the liner. Do NOT try this yourself: you do NOT have the equipment.

2. Drain in place, using ropes, a small sump pump, hoses, and a VERY large plastic tarp.

But . . . do what Carl said, first. It may not need to be drained.