Usually you will get an invitation to a meeting that has a URL, which you can use to participate in that specific meeting.  If you are unable to use the internet at the time of the meeting, the organizer can send you a call-in number to use with a phone.

…from a computer:

1. Find the email invitation the organizer sent you.

2. Click on the link to the URL in the invitation.

3. The first time you use it on your computer or device, you will have to download some software.  Click Yes, Always or Trust if prompted to accept the download.

4. If requested, enter the meeting password provided by your meeting organizer (the organizer decides whether or not to include a password). 

5. Put on your headphones/microphone.

You will enter into the meeting and the Attendee Control Panel and GoToMeeting Viewer window will appear.

…from an iPad, iPhone or Android device:

Tap the invitation link through an email or web page, or open the GoToMeeting app and enter your name and the meeting ID. If you do not have the GoToMeeting app, you can download the app from the Apple App Store or Google Play Store. You can also join by entering the meeting ID on the website.  Get your headphones/microphone ready.