The Victory Park is a big place. Its main pathway is lined with small booths selling a variety of souvenirs and foodstuffs (at least in summer). It contains several khachkars (cross-stones) and statues, including the impressive mother armenia statue that has the museum of war as its pedestal (I'm not sure if they are opening the museum anymore though). In the vicinity there's a forever burning torch in honor of fallen martyrs. The Park also contains the small Areni lake at the back side of the statue.
At the entrance, the path will start diverging, and you will need to take the one path that is not paved properly, you might even say it's not paved at all. (It used to be paved, but only the lining walls remain while the floor tiles have all but disappeared.)
Continue uphill and about halfway through you'll reach the cache location. This path was chosen because it's the least trafficked and less likely to be muggled.
The cache is a black MAGNETIC Nano, hidden somewhere where its magnetic capacity is used. Once you're there you will see it :)
This cache is the third in a series of 4, that will end with your victory in reaching the awesome mother armenia statue and the great view from the top.
Remember to bring your own pen.