Hi in addition to using tokens as was suggested you can template the body of the message by configuring alert_actions.conf For example you could have an alert_actions.conf (don't update the etc/system/default one) and add [email]
message.alert = Please fill this report in as follows\
Step 1\
Step 2\
\
And finally\
Step 3 I use the \ because you want the message.alert value to span multiple lines. That should get you something like the attached screenshot. More details here https://docs.splunk.com/Documentation/Splunk/latest/Admin/Alertactionsconf
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