Where can I find the join and replay links?

Manually

You can find the join and replay link manually for any registrant in their profile.  Go to the Registrants tab and click on any registrant in the list.  Then go to the History tab.  Once on the History tab click on the Webinar Name to collapse the details

Autoresponders

We pass the join and replay links to all autoresponders as custom fields.  

Below is a picture of Active Campaign but every autoresponder gets the same custom fields:

28 prefix is the Webinar ID

Webinar Date - the date they registered for the webinar

Webinar Time - the time they registered for the webinar 

Time Zone - The registrant time zone 

Live Room Join Link - the link to join the live webinar

Replay Room Join Link  - the link to join the replay

How would I use this in an automation/email?

Every autoresponder providers custom field variables/personalization tags that you can use in your emails.  In Active Campaign they look like this but you can reach out to your specific autoresponder to figure out what they are:

Are we able to turn off these fields?