You should add that the location of each titan build stage will be different for each race/faction, but it will all be under the military tech tree.
You also need the Titan Foundry. You will likely need to upgrade your Tactical Slots once or twice to build it, and it will set you back around 5000 credits, a thousand crystal, and a thousand metal.
Ive checked with every race, the total cost to build the titan and foundry, including research ,is 14,300 credits, 2000 metal, and 1500 crystal.
I recommend you save that amount up after getting the required amount of research facilities(4).
Build the foundry, and queue up all four stages of the research, then began building.