christy,
As has been said hopefully the bare wires will fit through the holes in the
screws and the covers willtighten down on them holding them in place.

Push them through so that the insulation on the wires meets the screws, andd
if you have wire cutters, cut off the extra wire maybe a quarter inch beyond
where it protrudes through the screws, leaving just the radius of the covers
available to be clampped.

If the wires won't fit through the screws even with a bit
more twisting, then you need ring terminals to put
on the ends of the wires. Actually you probably need "spade" terminals.
However these require to be crimpped onto the wires which needs tools you 
probably don't have.

Wrapping the wires round the screws and hoping they'll stay under the screw down
covers is the poorist way to do it, as you discovered
often the wires drift out from under the screws.

Hope this helps.

73s
Tom Fowle WA6IVG