If [ Expression 1 AND Expression 2]
#Do steps if true here
Where Expression 1 might be Field > 5 and Expression 2 might be Field < 10. You'll find a number of logical operators, and, not, or etc listed in the Specify Calculation dialog that you use to enter the expression(s) between the square brackets.
You can also nest "If's" for multiple sub choices:
If [rain = "yes"]
If [snow = "yes"]
Though the multiple sub-ifs can typically be turned into a CASE statement instead.