I'm going to take a stab at this while you sober up.
I am going to make the assumption that it still has the open loop cooling system. And not knowing what is (or isn't) there, I will start at the coolant bottle.
There should be a "T" on each of the lines just before the coolant bottle. If there isn't, you will need them. From each "T", you will need to run a hose to the two tubes from the heater core.
Before you do, you should check your heater core to make sure it isn't clogged or even worse, leaking.
A picture would greatly help.
1988 XJ 5 speed 4x4
Plain Jane beater with a heater