I presume you are Jew
You have to do "alya", i.e emigrate to Israel and then you will be enroled. There are some special conditions for lonly soldiers that don't have the family in Israel. You get some aid from ministry of defense and from some volunteer organizations. But no too much. You should prepare that the army is not just 3 years and then you continue your life as usual but have to serve every year for a period that can be a few days and even to a month depending on the unit you are in. Legaly until you are 45 years old but most soldiers get released in their 30's and don't serve until 45. If you don't show up when called you can stand to trial and go to jail. So you have to be very sure if this what you want. You can't come, try, and if you don't like it go back. It doesn't work like that with the army. Think well. Concerning age, you don't have to come at 18. You can enroll later too. I think until your late 20's. You don't have to be 18. So if you want to go to university first, you can do that.
