registration of more than one device

To ensure the accuracy of our responses we can only respond to support requests that are made in English. 

Could you please tell me step by step how I should proceed to register my map pilot license on multiple devices?

All you have to do is log into your account on the different device. It will tell you if you have devices available or not. 

Can't you have different usernames and passwords for each different device?

Users can have different accounts but you can only share your devices with their accounts if you are on the annual Pro or Elite plans using the "Team Device Sharing" system. The Base or monthly plans are not eligible for device sharing. 

https://www.mapsmadeeasy.com/map_pilot/