Not sure there is source on how to use it.

But how they work. Pretty simple to use in Icrew. Go to swap with the pot likely you normally would. Put in the rotation you want to drop and start date.
Now for the wild car. Wild card means give me anything. I would use wild cards to move trip over holidays that I would want off. So if I had a 3 day over Christmas lets say that started on the 24th ended 26th. My goal is to be done the 24th and have Christmas off. Here's an example of what it could look like. Notice my start date with the wild card allows me to be done on the 24th. You can plaster wild cards request all over the month in hopes to trading away a trip. No guarantee, it's like fishing, you might catch something and you might not. Also, a recommendation. When you go to "swap with the pot" start with number 2. All ways a good idea to leave number 1 open on any slip request you're doing. This way if trip(s) fall into open time and you really like one over the other you can open up number 1 aand add it in with out having to modify.

Remember, you're playing a math game with computer and reserve coverage or lack of coverage. You can see reserve coverage on Icrew too. And don't forget on the holiday and a day before and after are 1.5 times factor, all other days are 1.0. So if my 3 day trip on the 24th, reserve coverage on each day is as follows. -10, -10, -10. That is a total of -45 to the computer. That means you need to find a trip that has -45 or greater. Generally we are short on weekends and that's where you find trips that will work. You end up dropping your 3 day trip and picking up a 5 day trip to play the numbers game. Another good pointer, don't bid long trips over holidays, very hard to move because of the numbers. Shorter trips are easier to move in this case.
Hope this helps, sorry if it's confusing.