It's actually fairly simple.
First, fix any leaks or issues before starting. Since the hydrocarbon refrigerant is flammable, there is a small amount of increased risk associated with it. The risk is small but not zero. Mostly, the risk is that in a collision, the gas escaping from a damaged condenser could ignite. (There is also a tiny risk that gas escaping from a leaking evaporator could accumulate in the cabin and ignite explosively, but there have to be a very specific set of conditions for this to occur.)
For the existing R134a refrigerant charge, you'll need this removed. It is illegal to vent this to the atmosphere. However, most AC shops will discharge it for free since they get to recover and resell the refrigerant. In addition, you'll need to pull a vacuum on the system to purge any remaining refrigerant or air. Most AC shops will do this for a small fee.
Then it is as simple as adding 8 oz of R290/600a blend through the low pressure line. With the vacuum pulled on the line and the engine and AC off, simply invert the can and then squeeze the trigger and all of the liquid should get sucked into the system without ever having to use the compressor like you would for a refrigerant top off.
Here is the item I used:
https://www.duracool.com/shop/durac...acement-and-trigger-hose-assembly-attachment/
Comes with the hose and the exact amount of gas needed for the TJ.