Just like the other person said, you distribute. An easy way to remember how is the FOIL method. First, Outside, Inside, Last.
So for F, you'd multiply x and x, making x^2. For O, you'd multiply the first x and the 2, which gives you 2x, then for I, multiply the 3 and the second x, and you get 3x from that. Finally, for the L, multiply the 3 and 2, which is 6.
When the whole thing is "foiled," you end up with
x^2 + 2x + 3x + 6.
To put it in its simplest form, combine like terms. In this case, the 2x and 3x.
When you're finished, the expanded form should look like
x^2 + 5x + 6.
I hope that helped!