To share a map with someone else, you can use the share-icon and send a personal message.
Then you will see the following screen, where you can fill in the information that is needed to send it to someone. Choose the file type you want to send and click on 'Send'.
The paid subscription gives you the ability to send a Milkymap in Excel, PDF and PNG. With an Astronaut subscription you cannot send a Milkymap. Please visit the pricing page here to subscribe to a paid subscription.