Lift up all that foliage and look at the trunk- you will be able to see that all the yellowing leaves are on the lower part of the trunk. Just grab them one or two or three at a time and pull down and they will easily come off. It is totally normal for older leaves to yellow and need to be removed. If you leave them alone long enough they will fall off by themselves but the plants look so much better without them.

And always remember that this is not a palm, it's a tree native to Mexico, most often discussed as a succulent because of it's low moisture needs and caudex.