I want to add four bars of bass just to the intro; how?

I have a score written out in Musescore 2.0.2., and it looks great. However, I'd like to add a bass line consisting of four bars (only) for the intro. Those four bars for all other instruments are rests. I've tried doing this, but I end up with a bass clef through the arrangement. I only want the bass clef to show up for those four intro bars.

What do I do?

Thanks for the help,

Bob