My dad gave me a wizard lawn riding mower,and what happen was that,he lost his key and then he tried to straight wire it,he said it sparked,and after then it keep blowing the fuse when I try to crank it.what could be my problem?

Probably fried the wiring harness , or key switch.this kind of problem can be a burger,have to check the wires for a burnt one .check back of key switch for a burnt spot.sorry that's about the best I could do.Luck