cAdvisor exposes container statistics as Prometheus metrics out of the box. By default, these metrics are served under the /metrics HTTP endpoint. This endpoint may be customized by setting the -prometheus_endpoint command-line flag.
To monitor cAdvisor with Prometheus, simply configure one or more jobs in Prometheus which scrape the relevant cAdvisor processes at that metrics endpoint. For details, see Prometheus's Configuration documentation, as well as the Getting started guide.
CenturyLink Labs did an excellent write up on Monitoring Docker services with Prometheus +cAdvisor