To add air you will need a shock pump

Most shock pumps have a guide for the air to rider weight ratio which will tell you how much air to use. 

For your LMT'D air fork, 60 to 110 PSI is recommended, depending on rider weight and preference.

Alternatively, you can pump it until it provides the amount of dampening/stiffness you'd like, However you still want to use a shock pump for this, as the volume is significantly less than a pump for bike tires and can blow out the seals.

If you check the pressure of your shocks using your pump, please understand, some air will escape from the fork into the pump. It is better to judge the air pressure by performance. If you check your air pressure you will always find it is lower than when you most recently pumped it up.

If your shocks are leaking oil, it is likely that too much air was added or the method of inflation was not as advised. Upon arrival the fork will have approximately 135cc of 5-10 weight oil.  

If this is the case, please contact us with your order number, pictures of the affected area and a thorough description of the events leading up to the issue you are experiencing.

Fox, Rockshox, and other brands make shock pumps and should be available at your LBS or amazon! 

You can buy a shock pump here.