To use gates, both the origin and the destination must be a gate. In the case of colonies, the colony you are gating to / gating from must have the gate structure built.
Only under these conditions you can gate:
- both origin and destination have at least 24 control ticks
- both origin and destination are allied locations
- both origin and destination are unjammed
- origin and destination are within a 24 tick radius
- you have enough energy
You won't be able to gate into a conquered colony, but you can gate out of a conquered colony.
If you'd like to build gates, then build up your structures from:Beam weapons workshop >>> Explosive weapons workshop >>> Damage upgrade workshop >>> Range upgrade workshop >>> Teleport gate
You would then be able to teleport to and from your own colony as long as above requirements are met. You can also upgrade an outpost with full (at least 24) control ticks to a gate, it will cost 750 metal and 500 oil if I remember correctly. Wait for it to unjam and you'll be able to use it. Another option is to simply attack someone else's gate, and wait for 24 ticks to use it. Don't forget to jam the gate you're attacking, unless it has less than 24 control ticks!