As any other icon pack in Google Play Store Rollerduck requires a custom launcher for its work. Besides those tested launchers mentioned on Info page it should be compatible with many others. Note: most stock launchers don't support custom icon packs!
Some of launchers support direct apply and some don't. If you experience difficulties in applying Rollerduck icons from within the app do it in settings of your current launcher. For instance go to:
Action Settings > Appearance > Icon Pack
ADW Settings > Icon Appearance> Icon Set
Nova Settings > Look and feel > Icon style > Icon theme
etc...
In favour of style it's recommended turning off adaptive icons support and icon labels in launcher settings.
There is wide choice in Alternative section of the app. Please, try to find a substitute there if some of preinstalled apps of your device don't have themed icons. You can use them as custom folders also instead of boring folder-shape-folders. To change icon longpress it on your homescreen or in the app drawer and click Edit, then use search by name and choose.
Please, use Icon Request Tool in the app if you miss some essential preinstalled app icons.
You can place Analog Clock Widget on your homescreen by pressing on its empty space and clicking Add Widget (in certain launchers may vary)
Wallpapers are available in two variants to chose from:
torn edges
smooth edges