You can use the Random(x) expression to get a random number. To get a number within that range, you would subtract from your private variable -- using the subtract from private variable action -- this expression:
Random(10) + 1
One thing to know about the Random(x) expression is that it returns one of x possible numbers, from 0 up to, but not including, x. So Random(10) will return a value in the range of 0-9. Thus, adding 1 to this will bring the minimum up to 1 and the maximum to 10.