Add merge fields in the invite screen by clicking the 'i' (information icon) under 'Body'.
Copy the merge fields you wish to add into the body of the email to populate the information (e.g. copy [myMobile] if you wish to populate your mobile number into the email that you write).
Then paste the merge fields in the email wherever you wish (e.g. paste [myMobile] at the end so they can reach out to you).
Note: Be careful to make sure it is exactly copied- they are case and space sensitive!