There should be a petcock valve in the lower middle of that radiator. Here's a picture; it's the white gizmo at the bottom. Take the radiator cap off before opening the petcock to allow complete draining.
Zerex Asian and Mak SuperKool are a few brands that have compatible coolant that you should be able to find locally. Or you can get the genuine OEM stuff, but it is likely to be expensive. It is very important to get the proper compatible coolant for this vehicle, as diesel coolants sometimes have additives to prevent cavitation (small bubbles) and erosion of wetted parts caused by the "knocking" sharpness of high compression diesel engines.
The proportions are probably safe at 50/50, but in a very hot climate you may be able to use more water and less coolant. The coolant bottle will direct the proportions based on your climate range.
After you refill, you'll want to run the vehicle at idle with the radiator cap OFF and the heater ON, until you no longer see any bubbles in the filler neck. If there is no radiator cap, there may be a small bleed screw on the thermostat housing. You can crack this open (only a few turns) until you no longer see bubbles or foam coming out. I'm pretty sure your radiator will have a cap and a filler neck.
After this, the coolant level has probably dropped as the air has been bled out and replaced with the coolant mixture. Turn the vehicle off, let it cool for a while, and top up at the radiator neck. Also make sure the overflow reservoir has the proper level.
Clean up your mess as there is sure to be some, and dispose of the used coolant properly - it really shouldn't be dumped on the ground.
That should do it! Good luck. As the previous poster mentioned, it's not hard to do - just take your time.