Preparing a very short presentation for a PhD interview
It sound like you need to give an elevator pitch with slides. Short presentations are tough! You need to follow their instructions exactly and describe both a project and your fit to the program. You need to have this in mind: this is a sales pitch, so be short and to the point.

The objective is to sell yourself, so details on the project matter less than how you contributed in a way that’s relevant to the PhD program you’re applying to. So if your program is on graphic design focus on how your designs were used in the project, if it’s programming, focus on your code contribution etc. 

In the part about you, try to show that you’ll be an amazing fit to the program: high-level plans, your agenda, your vision etc. you need to convince the committee that you’ll be a valuable asset to the program.

You must practice your talk several times till it’s perfect, and ask your friends to listen to it!

While conference talks are different, I highly recommend Simon Peyton Jones’ advice on how to give great talks, here: https://www.microsoft.com/en-us/research/academic-program/give-great-research-talk/

Good luck!