What it means when people say "cool story bro" is that whatever you have been talking about is interesting. Some people might say "cool story bro" in order to close that story and change the subject.
cool story bro.
Cool story bro.
cool story bro
Cool story, bro.
Cool Story Bro.
cool story bro
hah, Cool story, bro.
cool story bro tell it again
cool story bro.
''Cool story bro, don't wanna hear it, go tell it to your pillow''
Cool story bro, it needs more dragons.
cool story bro