(This is the English Only forum. If you would like a translation to Spanish you may post a question in the Vocabulario General forum.)
"Saddling up" is getting your horse ready to ride. It sounds like a quote from a American Western. To saddle up, figuratively, means to get ready to do something. "Being scared to death" is being the most frightened you can possibly be.
The saying means that courage is the ability to do something in spite of your fear.