If you check the Settings module and go to Content -> Media you can configure what file extensions could be uploaded to the Media library.
It could be that you should also need to change the max allowed file size
https://docs.kentico.com/k12/configuring-kentico/configuring-the-environment-for-content-editors/configuring-media-libraries#Configuringmedialibraries-Configuringmaximumfileuploadsizeinmedialibraries
And depending on your hosting settings you might need to add the file type to be able to serve it
https://docs.microsoft.com/en-us/iis/configuration/system.webserver/security/requestfiltering/fileextensions/