First, if you live in town, be very careful practicing in your back yard. All it will take is one loose arrow to go through or into a fence and you may get a visit from the PD. Second the type of target composition will depend on shooting field points or broad heads. Stay away from plywood/ lumber and even stacked corrugated as far as targets. Your arrows will either break going into the material or be in there so tight that you will either break or bend your shaft getting it out. Styrofoam just disintegrates after one shot so that won't work either. Buy some quality targets to practice with. Just plan on what you are going to shoot before you buy, field points or broad heads because target composition is different for each one. Also remember your arrow and tip will be used again, hopefully, not like ammo in a rifle that gets used once. The idea is to reuse them as long as possible.
As a side note about your equipment, have it checked out at a reputable bow shop to verify that it is sound, no cracks in limbs, pulley issues and string wear. Also verify that it has the correct to fit your body as far as draw length. If poundage can be adjusted, I suggest that it is turned down to 40 or 50 pounds till you get proficient with it then reset poundage to what you would want to pull back on in the future. Also a good time to ask a lot of questions at the bow shop as far archery goes like actually tuning your set up to shoot consistently.
All this is just a start, it will be fun and addicting as you progress. Although learning and or doing it incorrectly may be frustrating and or unsafe.