Just drag and drop files in the browser window, then create a link for sharing. You will need an account to create a link. To streamline the process for new users you can start uploading as soon as you access the website and create an account while it's uploading.
All files uploaded to Mega are first encrypted on the users side. To access files a decryption key must be supplied. For ease of use, the decryption key can be appended to the URL you share.
Higher than normal chance of a forced service shutdown
Mega has a higher than normal chance of having legal troubles due its founders past, thus there's a higher than normal chance that the service may be shut down with all your files in it and no way to retrieve them.