On the package page, “Proxy access” shows the host, the port, the username and the password, and builds proxy lines in the format your tool expects: host, port, user and password in the order it wants, or a full proxy URL. Copy a line into any browser, bot or script that takes an HTTP proxy with a username and password. HTTPS websites work through it.
The username is what tells the network which package the traffic belongs to, and the password carries the targeting (country and session) the page adds for you. Use the lines as the page builds them.
To check that it works, run the command printed on the package page. It prints the IP address your request left from.
curl -x http://USER:PASS@HOST:PORT https://api.ipify.org