Solving Unknowns for 10 N Force and 3.0 kg Box

[xCanx]

I'm having trouble finding the unknowns for this problem.

There is a picture of a box and m=3.0 kg

F1 is pushing to the right and 10 N is pushing to the left.

I have to find Fnet and a.

btw, It is free body diagram.

 

[xCanx]

can someone tell me the first step?