Adobe Flash Player can't be installed without Administrator privileges. You need to ask someone who gave you the computer if you want to install something (if it's a teacher/lecturer or someone similar, asking for it is a BAD idea especially because of watching videos @ crunchyroll.com, unless the PC IS FULLY YOURS, not because of borrowing or else)
If you think you can't do what I mentioned above, you might need to use your own PC anyway.