Q: been trying to download after download and says may not have privelgies

I could noeeeeet get into itunes so I deleted and thn tried to reinstall. Since thn after the download all I see it come to a point whre it cannot complete it. says I may not have all the privelgies. Then after retrying numerous times all I can do is abort.I back out of the download. How can I move forward and get this reinstalled