this can be done in 3 places, same effect.
1)left side of ship/structure circle on planet
2)empire symbol in empire tree, in concerned gravity well
3 )your "ships" dots - the ones farther to the right, if there are structures in-well, in the empire tree
one click = combat (including scouts)
two clicks = strikecraft (both bombers and fighters)
three clicks = if in well, colony frigs, if they aren't in well, back to combat ships