In the link you mentioned, you can see that you run your container as
docker run -d --name bitwarden -v /bw-data/:/data/ -p 80:80 bitwardenrs/server:latest
This means that the container itself exposes port 80, which in turn is mapped to port 80 on the host.
In other words, you access it as http://ip_of_your_host.
Please note that you may already have something on port 80 (typically a web server), in such a case you will need to change the mapping to, for instance, -p 9090:80 and you would then access the container via http://ip_of_your_host:9090