There are a few ways to lift your Jeep YJ. The easiest would be to put on some greasable shackles for a yj. The are made slightly longer than stock, and will raise your Jeep about an inch.
The next way to lift your YJ would be to add a body lift. A body lift will replace the worn out rubber spacers that are currently under your Wrangler with new ones that are larger. This will lift the body off of the frame up to 2 inches (they come in 1 or 2 inch body lift kits). These are fairly easy to install, once you break loose the rusted bolts – penetrating lubricant applied the day before will help.
The last way to raise your YJ is a full blown suspension lift. A suspension lift will replace your existing leaf springs with new ones that have more arch. You will also get new shocks, and possibly some steering components, depending on the amount of lift you are going for. Wrangler suspension lifts can be difficult to install, but it is something a shadetree mechanic can do over a weekend with normal hand tools.