It is without a doubt a California king snake. Non-VENOMOUS (there is no such thing as a poisonous snake)
And I cannot believe that I am the first to say this.. what the hell are you doing with a snake that you don't even know if it is venomous or not!?
Clearly you have access to the internet... so it really is NOT that hard to do a little research about an animal BEFORE you get it! Even just enough to know what it is!
what makes you think it is ok to just go out and get any random animal you feel like without knowing it's care requirements, and whether it can kill you or not!?
what if it was a sea krait or other deadly venomous animal, what would you do with it then? Something tells me you do NOT have the experience to be working with hots so you would be pretty much SOL.
Maybe next time put just an ounce of thought into your plans before you proceed....
Now that the important part is out of the way....
You lucked out with it being an easy and harmless snake to care for. Cali kings are hardy animals, can be kept in a 20 gallon long tank, with an under tank heater, a water bowl and a hide, fed appropriately sized mice or rats once a week, and thats about all there is to it. Most of them are calm and easy to handle as well.