Account items such as content packs, PLEX and items purchased through the New Eden Store, are delivered to the account’s Redeeming System. These items can be redeemed by accessing the "Redeemable Items" screen, accessible from the bottom of the character selection page.
Alternatively, they can be redeemed through the NEOCOM -> Inventory -> Redeem Items section.
Also a default shortcut of ALT-Y can be used to open the redeemable items screen.
Lastly it is possible to return PLEX back into the redeeming system. This is done by right clicking on the PLEX located in the hangar and selecting the "Reverse Redeem" option. The PLEX can then only be redeemed back to its former station. More information on Reverse redeeming can be found here.