The Corellia Yellow Presence Datacron is located in the Government District map on Corellia grants Presence +4.
The closest Republic quick travel point is the Port Paveria, or Uptown if you don't have it quick travel point and the closest taxi is the Uptown Tram speeder point, both in the top right of the map.
The closest Imperial quick travel point is the Business Sector quick travel point and the closest taxi is the Business Sector Tram speeder point, both in the top right of the map.
The Corellia Yellow datacron is in the Port Paveria and is available to both Imperial and Republic players. Finding this datacron will give you a permanent stat boost of Presence +4 to all your characters on your server, and will unlock the Galactic History 80: A Return from Exile codex.
Corellia Presence +4 Datacron (Both Factions)
Quicktravel: Port Paveria, or Uptown if you don't have it / Business Sector
Taxi: Uptown Tram / Business Sector Tram
Location: Government District - Port Paveria
Difficulty: Easy - Small jump
Codex: Galactic History 80: A Return from Exile
How to Get the Corellia Yellow Presence Datacron
Republic players can just walk in to this datacron, Imperial players will need to run or fight their way in as the enemies will be hostile.
Quick Travel / Taxi
The [HEROIC 2+] Prison Busting heroic shuttle is a little bit closer.
Walk into Port Paveria in the tunnel
Fall down onto the circular pipe
Slowly walk your way off of the platforms onto the center circular pipes down below. To make this fall easier, turn walk on by pressing the slash key above the numberpad on the right hand side of your keyboard. The datacron will be at the very end of this long pipe under the main platform.