You can activate them by pressing the Harvest/NPC chat (default is space bar) to grant certain bonuses such as boosted recovery, reduced cooldowns, or special effects like summoning lightning or poison clouds. All runes also grant 2x EXP while active. Runes have a 15-minute cooldown between usage.
If you don't use a rune and leave it sitting, the rune will become cursed and reduce EXP/drops to 0 over time. You can reverse this simply by activating the rune. Activating a rune also grants a special buff that lets you ignore the rune curse in other maps, if you happen to leave the map you're in.
PC Game Supply, assuming this was the site you're trying to use, is a third-party service, and has nothing to do with Nexon.
You should contact their support center if you're unable to login: on their main page click "Support" on the right side of the ribbon at the top of the page.
