I cant seem to open the .app for my explode arena. is there some directory to place it in? or some way to install it into my HP?

What kind of application is this game? What is this HP you're refering to?

Series 60 v3 is incompatible with applications written for Series 60 v2, so any games which are Series 60 apps won't work unless re-written specifically.

Java games should work unaltered, but a lot have issues with the higher screen resolution of the N73. The phone does not scale it's screen to match the lower resolution the Java app. expects, so only a portion of the screen is used.

"HP" could be "handphone" = the phone. Most probably it is not referring to Hewlett-Packard, for example. ;)

I cant seem to open the .app for my explode arena. is there some directory to place it in? or some way to install it into my HP?

More clear, please:) Explode arena, is a sis game. Is that:con? HP? Wich HP:con?

No .app file is supported in S60 3rd Edition any more, that includes N71 and N73.

You may need to check the company that develop the game and see whether they have new version for S60 3rd Edition or not.

Btw, N/A is correct, HP is "Hand Phone".
People from some countries, such as my home country Indonesia, are still referring mobile phone as "hand phone"... :)