Dear Juanjo,

Standard this is not possible.  When you click import you get a link to Odoo its's FAQ regarding import. This will explain more for you 

You might be able to find a module in the app store that can do this. 

In V13 it is possible to link a google calendar within the settings. There is also a manual available for this. YOu can create a google account for free and upload your .ics file there and then link it to your Odoo.

Hope this helps you