In Path of Exile, gems include Active Skill gems and Support Skill gems. Gems must be equipped in item sockets before their use. Active skill gems grant an active skill for the player to use and are further augmented by linked support skill gems.
This is a Skill Up challenge. It is very easy.
Note that in order to complete this challenge, you must use Active skill gems. Support gems do not have any effect.
As the following example shown, I put six Active skill gems into my equipments and completed this challenge.