Go into the config.
minecraft\config\biomesoplenty\biomegen.cfg
for the modpack.
Open that file, and just start setting biomes you want to true, and ones you don't want to false.
####################
# biomes to generate
####################
"biomes to generate" {
B:Alps=false
B:Arctic=false
B:AutumnHills=false
B:Badlands=true
B:BambooForest=false
B:Bayou=false
B:BirchForest=false
B:Bog=false
B:BorealForest=true
etcetcetcetcetcetcetc.........
Note the more you have to true the rarer some biomes may become as there all cluttering for space, you could go 1000's of blocks and not find some biomes if you have them all on. Really recommend having just a small handful of ones you really like and leave out the rest.