To make your frosting thicker, you can add an extra 2-3 tablespoons of powdered sugar (always start with less but add more if needed). Cream cheese frosting will thicken as it sits in the refrigerator. I recommend covering it with a lid and setting it in the refrigerator for 20-30 minutes if you plan on piping it, this is a good alternative to adding more sugar. You can also thicken it with cornstarch if you'd rather not sweeten the frosting more than you have to. Keep in mind that adding too much cornstarch can make the frosting gummy, which is the exact opposite of what you want! Slowly incorporate a Tablespoon's worth of cornstarch into the frosting, adding more if needed, until you reach your desired consistency.