There are so many tools for making video calls online. Here are some of them and links to help you get started.
Zoom is a powerful, business focussed video platform. On it’s free package it can host meetings of 100 people for maximum of 40 minutes.
Full information and support is available at https://zoom.us/
There are also a number of support articles to get you going at https://support.skype.com/en/skype/all/
WhatsApp is not just for text messaging. You can use it for video calling too. Careful though, if you are not connected to Wifi, it will use your mobile phone data package which could get very expensive!
Read more at https://faq.whatsapp.com/
Facetime is reliable and easy to use app, but it is limited to everyone using and Apple iPhone, iPad or Mac.