How do I personalize an email with the recipient's first name?

Short answer: Use “Insert Field” in the subject or in the body. The field is replaced, recipient by recipient, when the email goes out.

Steps

Open an email template, or compose an email from the Contacts page.
Put the cursor where you want it, in the subject or in the body.
Click “Insert Field” and choose the field from one of the three families: Contact, Account or Shop.
The field is inserted as a code between double braces. Leave it as it is: it gets replaced when the email goes out.

What each family holds

Contact — the recipient's first name, last name and email address.
Account — the name of your organisation.
Shop — the name and the link of the shop.

The unsubscribe link is not in that list, and that is deliberate: DAGOBA adds it to every one of your emailings automatically. You never have to place it yourself.

The Shop field asks you which shop

As soon as your email uses a shop's name or link, the send window asks you to name the shop concerned, in the “Shop concerned” section. Every recipient will see that one shop. Until the choice is made, sending stays blocked with the note “Tell us which shop this email is about.”

The shop link is inserted already formatted as a clickable link. Nothing needs to be added around it.

Checking before you send

A merge field is only replaced when the email goes out: in the editor you see the code, not the value. To check the real result, send yourself the email by picking yourself as the only recipient.

Going further

You'll know it worked when: Each recipient gets the email with their own value in place of the inserted field.