When accessing a conference call with via phone you would need to enter either an access code or a moderator pin after calling the dial-in number.
The moderator pin is reserved for the account holder or those in charge of hosting or moderating the call (you can have more than one host/moderator on a call). After entering in your moderator pin you will gain access to the moderator controls where you can mute others, initiate recording (for those with upgraded packages) via phone.
Additionally, you will need the moderator PIN to open up a conference call if you have the Waiting Room turned on.
To join a call as moderator via internet, just ensure you are logged into your account and join as you usually would within your browser or app.
Only one person can be logged into your account at a time while also being connected to the conference via web. This support article explains how you can have multiple moderators connected via web.
Please keep in mind, you do not need to begin a call by entering in a moderator pin, you can also start a call by using the access code if you don't have the Waiting Room feature active.