Gratis' suggestion to clear inactive results may work easier, Heather. I don't know LimeWire well enough yet to be able to help with that way.
Otherwise, this other way works for me. The reason it is so complicated is that it is for people who want to persevere with things that are downloading but too gradually. It does this by trashing things that are not downloading at all and just clogging up the system.
There may be a way to do this from the "Library" window in Limewire.
This other way, described here, doesn't use that "Library" window at all. Inside LimeWire, it uses the main LimeWire window, where you have the list of all the downloads that are queued. Outside LimeWire, it uses the "Incomplete" folder that is on the computer's hard disc.
On a mac, you get to that Incomplete folder outside LimeWire, using the Finder, which is what shows up on the menu bar at the top of the screen after you have clicked once on the desktop. You can also go to the Finder on a mac by holding down the command key (next to the space bar) and pressing the tab key repeatedly until you get on the blue smiley face, then letting go. A third way is to click once on the blue smiley face in the dock, at the bottom of the screen.
In the Finder, under File, choose "Find". Where it says "Search in", the no-brainer is "Everywhere". Where it says "Name contains", type "Incomplete" and click "Search". You will get a list. Double-click on the folder whose name is "Incomplete". That will give you the window for that folder.
In my first post I said "see what it says at the bottom of the window" but since updating my system I see now that the info to check is at the top of the window. On my computer, LimeWire slows down when there are more than 2,000 files in that folder. Older computers may slow down with fewer. If there are not many files in that folder, this way may not do much.
Please note that the other tips in the LimeWire manual (currently at
http://www.limewire.com/english/content/userguide.shtml) are more important to try first. I resort to the method here when those things are not enough.