It is recommended to use plugin loco translate for easy translations, below is the manual way.
To translate emails using Translatepress, you will need to include translated text inside shortcode [trp_language language="en_US"][/trp_language] , where language attribute holds the value of "locale code."
You can find the list of "Locale code" here
For example:- To translate email subject, go to email settings and under "Subject" option, add this
[trp_language language="en_US"]This subject is in English[/trp_language]
[trp_language language="fr_FR"]This subject is in French[/trp_language]
You can do the same for other email content fields.
Id - Product ID
Inline Toggle [xoo_wl_form id="10" type="inline_toggle" text="Join Waitlist"]
Popup [xoo_wl_form id="10" type="popup"]
Inline [xoo_wl_form id="10" type="inline"]