To obtain the Grakata you have two options, being the first one to buy it through the Market Console o directly from your Arsenal of your ships. It will cost you 125 Platinum, but if you choose this option you will also receive a weapon slot in your inventory and an Orokin Catalyst already installed.
The second option is to buy the Grakata Blueprint in the Market Console and craft it in the Foundry of your ship. To do that you will need the required resources to start the process. Do not forget this requires time and effort.