Cannot delate items on my desktop without admin's password and username!

Okay so yesterday I was getting rid of some files of my desktop of the computer I use almost daily so it would not be huge in memory like images, and hew other items and I tried putting them in my trash so I can get rid of them, but it said well this:



I'm not the admin on this computer far from it, only a regular member.

PLEASE HELP!

Caleb531 said:

It looks like you don't have the privileges to delete those files. You should contact your Mac's administrator (whoever it is) about it, and see if they can help you.

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But big help, but he was able to get rid of files I wanted, but I want to remove files without waiting my dad to come home, and type his password every freaking time I want to delete something. I can only delete files IF I added them to my desktop on the day that I added them. Not sure about getting the file, signing out, signing back in them getting rid of it. But I do not want to try it out because my ada will possibly get angry.