iCloud storage is almost exclusively for storing backups of your phone and iPad. While you can use it to store documents for many of the Apple Apps (e.g.: Pages, Numbers, Keynote, etc), it doesn't really help to free up space on your device.
But here are some things to try:
1) Identify what can be deleted from your device.
To see a list of apps sorted by storage consumption, open Settings -> General -> Usage -> Manage Storage.
If there's an app that you're not using, you can delete it by tapping on it in this list and then tapping Delete App.
2) Delete music
To selectively delete songs you don’t listen to, you can open the Music app, go to any song list view and swipe from right to left on any song. A delete button should appear, which, when tapped, should remove the song from your device.
3) Subscribe to iTunes Match
This allows you to keep all your music in the cloud. The idea would be to keep large music libraries in the cloud, only keeping local copies of the music when you're using them:
4) Delete old Podcasts
If you listen to Podcasts, you can delete old episodes by going to Settings -> General -> Usage -> Podcasts and tapping the Edit button.