To get Gmeet URL, firstly you have to login to your gmail account. If you are not logged into gmail, click on the sign in button. Then go to https://meet.google.com/ then click on New meeting button and then select Get a meeting link to share link on selecting this link it will open a modal from here you will get Gmeet URL, just copy this Gmeet URl and paste it in Smart School Gmeet URl field.

Gmeet Url first Image
Get meeting link to share image
Gmeet Meeting URL image