Press / in the editor and pick Map.
The box at the top is already filled in with what you have written so far, because you have usually just described the trip in the post itself. Edit it however you like — or replace it entirely:
2 weeks in France: Paris, Strasbourg, Lyon, Arles, Marseille, Nice
Press Create map and it draws the route, drops the pins and inserts the card into your post. That is the whole flow.
You can also name a trip loosely rather than listing stops — "a week road tripping the Ring Road in Iceland" — and it will work out a sensible route.
Reusing a map you already made
Everything you have made is underneath, with a thumbnail and the number of places. Click one to drop it into this post. A map about the same trip belongs in every post about that trip; there is no reason to make it twice.
Editing a map
Edit it in the post, on the card itself: rename the trip, rename a place or rewrite its description, move a place up or down the route, move a pin that landed in the wrong square, add somewhere it missed, delete somewhere you did not go. Hover a place and the controls for moving or removing it appear.
There is no Save button. A map is not part of your post — it is its own thing that the post points at — so edits save themselves, and they save whether or not you save the post.
Which is also why edits follow the map everywhere it is embedded: fixing a pin fixes it in every post that uses it. Only your own maps are editable this way; someone else's map in your post is shown, not offered.
Two things live in the dashboard instead, under AI Blogger → Magic Maps: how many days the trip took, and deleting a map outright.
Your maps also appear publicly under Itineraries on your profile, which is worth knowing before you map a trip you would rather not publish.
What it costs
Making a map costs around 600 AI credits — one of the cheapest things you can spend them on. Reusing one you already made costs nothing — another reason to embed the same map in the whole series rather than generating one per post.
Check the pins
The route is worked out from place names, and place names are ambiguous. There is more than one Springfield, more than one San José, and small villages are often guessed from the nearest larger town.
Open the map and look at it before you publish. Fixing one pin takes a few seconds; publishing a map that puts your hotel in the wrong country is the sort of thing readers remember.