I have two kids and I don't know how to get them to obey me.
That doesn't make you a "bad parent". Parenting skills can be different from person to person.
Yeah, I have tried everything.  I tried timeouts but maybe I did it wrong.
Have you considered PMT or Parent Management Training? It can help teach positive reinforcement methods for improving common behavior issues.
I have never even heard of PMT.  Where can I take Parent Management Training courses?
There are several institutions that offer the course. I am sure you could find a local resource by searching online.
I will have to check them out.  What do you learn at PMT classes?
You can learn about positive reinforcement methods, how to change your own parenting behaviors, and how to handle tantrums. Among other things.