Downloading Adobe.

Hello,
Well. I've been on youtube for a while now. I haven't been able to watch videos.It tells me to download Adobe Flasherplayer(The latest one). So. I try to download it and try to open it (i have mozilla firefox) and it says i need to close Firefox.So i close it and click try again.Still doesn't work.So...I tried Internet Explorer and it just fails. I've tried every troubleshoot is suggests and it still doesn't work.
I truely need help i feel very upset about this. Anybody have any idea how to help me?