Is it safe??
Yes, of course! :)
There is no way it's a virus so just watching some good old hulu isn't gonna hurt you.
Literally billions of computers all over the world have flash player, it's needed to watch videos on YouTube, play flash games, just about every website on the web uses it.
But to make sure you're not getting a fake flash player,
be sure you download it from the -official- website here:
http://www.adobe.com/go/getflashplayer
and you're all set!
For anything else you need to know about viruses, try asking your friends that know about computer stuff or doing a google search, it'll help you figure out what's bad or not.
Soon enough you'll build a collection of websites that you can always trust and count on!
Good luck in the future with getting around the world wide web! :D