How do you get a liger?

Crossing a male lion with a female tiger produces a liger. Conversely, A male tiger crossed with a female lion produces a tigon.
Ownership-wise, it is virtually impossible, and not recommended. Ligers are captive bred, and like any exotic animal you need to have a license to own one.

Getting one simply because "you really love them" is a horrible excuse to own one (and there is no excuse). They are extremely dangerous, and even though they don't occur naturally in the wild, they are still wild animals and are therefore unpredictable. Even a "friendly" liger is dangerous, for they are very powerful animals and could kill a human easily by simply giving a playful swat. This holds true for ANY large cat/large animal.

If you mean "How do ligers get created" then the answer is by breeding a male lion with a female tiger.