upgrade a weapon

ok, so i have unlocked a bow string that I want to put on another bow, i think its like a crippling string. how do i attach that to my other bow in role playing mode????

You unlocked it with you PVP only character? If that the case, no you won't be able to use it on your PVE char.

If that wasn't the case, then all you need to do is just double click the string and click on the bow you wish to upgrade.

Note that some items - preorders, greens and quest rewards (?) - cannot be upgraded.

Also, upgrades will overwrite existing upgrades. So if the bow already has a prefix ("sundering bow of fortitude") you'd be replacing that prefix with the "crippling" prefix.

assuming the bow string you want to use is on another of your PvE characters, you use the following steps;

1) expert salvage the bow string off it's current bow
2) double-click the bow string
3) single-click the bow you want to put the string onto

if the unlock was achieved via an item unlock code from ANet or by spending Balthazar faction at a priest of Balthazar, then you cannot upgrade a PvE weapon with it.