I bought 15 meters of the Cotton rich flece from SL the other day LOL.

GiGi- to thread your overlocker why not try the tie & pull method. Cut your already threaded thread at the top so its still threaded & turn all of your tension knobs to 0 & then tie your new thread to the ends of your old then pull the old thread through the machine at the needles. Do it gently & your thread will go through the machine & your new will thread in its place KWIM? Just remember to turn your tension to 0 & then back to its normal settings before trying to use it.
Its how I do mine.