You can obtain runes by killing Bosses, completing quests or from other tasks. To use the rune, drag it and place it on the desired item.
Note: Runes are divided in 3 tiers of rarity,  Common, Uncommon and Rare.

Poisoned : Deals Poison I to III for 1.00 to 4.00 seconds.

Sedating : Deals Slowness I to III for 1.00 to 4.00 seconds.

Blinding : Deals Blindness I to III for 1.00 to 4.00 seconds.

Flaming : Sets enemies on fire for 1.00 to 4.00 seconds.

Vampiric : Heals you for 5.00% to 12.00% of damage dealt.

Recursive : Increases ranged damage by 1.00 to 4.00.

Hooked : Reverses knockback and modifies to 30.0% to 80.0%.

Heavy : Increases knockback by 10.0% to 50.0%.

Of the Fleet-footed : Every 2-4 hits, grants Speed I-IV for 1.00 – 6.00 seconds.

Of Hunting : Increases ranged damage against mobs by 1.00 to 8.00.

Of Mending : Passively regenerates durability over time. Note : 1 durability per 5 seconds when held.