There are many ways to do it, and it depends entirely on the size of files you are working with. Do a quick Google search and you'll find many solutions.
If you're looking to upload large files, you'll want to look into AJAX calls and file chunking using something like ReadAsArrayBuffer.
For starters, go here:
http://stackoverflow.com/questions/5193842/file-upload-asp-net-mvc-3-0
or here:
https://cmatskas.com/upload-files-in-asp-net-mvc-with-javascript-and-c/