Demolition chge [fix]

[jivemi]

Hi folks. I'm playing the "Baptism of the Black Brigade" campaign. In the second scenario deployment screen there are two demolition charges placed on bridge hexes. Both include the label "[fix]."

My question is, What do I need to "fix" these demo charges, or does "fix" simply mean they're fixed in place, and all I gotta do is press the f-key to blow them up (preferably with a whole bunch of enemy units on them )? Thanks for your kind attention.