Hero's Arms is kind of a good-old Zelda-like adventure game. Defeat monsters along the way of the outside world to find dungeons where quest items (or treasures) are kept safe by big monsters. Those relics are then used to grant passage to the evil Gordzak's lair, which you'll have to destroy in order to beat the game. To accomplish this you will need to upgrade your gear and your personal strength by leveling up and finding magic items. Have fun!
Use the Arrows Keys (or W,A,S,D) to move around and navigate in the inventory screen. Space Bar to bring up the inventory. Z or N to attack (confirm in menus). X or M to perform magical attack (cancel in menus). You can change the quality in the inventory screen.