Floribunda roses have many flowers that bloom simultaneously on the same cluster and ar known for their prolific blooming.
Begin by cutting out very old shoots, shoots that are diseased or dying and badly placed shoots. Then shorten the remaining shoots to about 45cm (18in).
Floribunda roses often look more twiggy than hybrid teas. After you have removed unhealthy shoots, start pruning from one side and then work your way across.
Then, begin cutting out dead or diseased shoots to a point just above a healthy bud close to the base.
Remove crossing or badly placed branches, remove very thin and spindly shoots coming from near the base.
Here is a floribunda iceberg rose in my front yard that I already pruned, you can start to see the new growth. This is something like what your floribunda rose bush will look like, the perfect framework for new growth.
A closeup of the white iceberg rose above at the point of pruning.