On the right-hand panel, fill in the internal email name and subject (you can change it later);
Save the email;
Go to the Advanced tab;
Paste your email code in the field HTML Code; (If you are coding your email in MJML, you can’t paste it directly, you will need to convert it first. You can use this free tool to generate the HTML from your MJML by clicking here)
I recommend auto-generating the plain text version by clicking the Auto generate button;