The Radarr team does not offer an official Docker image. However, a number of third parties have created and maintain their own.
These instructions provide generic guidance that should apply to any Radarr Docker image.
Synology Users can see TRaSH's Synology Docker Guide
Portainer should be avoided for setting up docker containers
See this Docker Guide and TRaSH's Docker Tutorial instead for how to setup Docker Compose.
There are two common problems with Docker volumes: Paths that differ between the Radarr and download client container and paths that prevent fast moves and hard links.
The first is a problem because the download client will report a download's path as /torrents/My.Movie.2018/, but in the Radarr container that might be at /downloads/My.Movie.2018/. The second is a performance issue and causes problems for seeding torrents. Both problems can be solved with well planned, consistent paths.
Most Docker images suggest paths like /movies and /downloads. This causes slow moves and doesn't allow hard links because they are considered two different file systems inside the container. Some also recommend paths for the download client container that are different from the Radarr container, like /torrents.
The best solution is to use a single, common volume inside the containers, such as /data. Your Movies would be in /data/Movies, torrents in /data/downloads/torrents and/or usenet downloads in /data/downloads/usenet.
If this advice is not followed, you may have to configure a Remote Path Mapping in the Radarr web UI (Settings › Download Clients).
Permissions and ownership of files is one of the most common problems for Radarr users, both inside and outside Docker. Most images have environment variables that can be used to override the default user, group and umask, you should decide this before setting up all of your containers. The recommendation is to use a common group for all related containers so that each container can use the shared group permissions to read and write files on the mounted volumes.
Keep in mind that Radarr will need read and write to the download folders as well as the final folders.
For a more detailed explanation of these issues, see The Best Docker Setup and Docker Guide wiki article.
To install and use these Docker images, you will need to keep the above in mind while following their documentation. There are many ways to manage Docker images and containers too, so installation and maintenance of them will depend on the route you choose.