Just unlocked some new shouts.. And i want to know how to learn the other words to lvl the shout up Where to find/get/learn them..!?

go exploring...word walls can be anywhere...some are even out in the open...be prepared to fight for those though

Do you need to do the greybeards mission before you can learn new shouts? I've now got a new dragon soul, and a new shout to learn, but somehow I can't learn it.

Maybe...not sure....i just didn't bother trying to learn more until after that so i can't tell you for sure

I'm still tryingt o understand this too. I have two shouts I cant use. Already talked to the greybeards and ironically they literally told me there is nothing more than can teach me. I know I need to absorb dragon souls, I've defeated some dragons, absorbed their souls.. nothing. Hmmm. Maybe I missed something.

You have to press R on the shout i guess.. Left in the corner you have the options menu.. [R]-Unlock
I don't think you need to do the greybeards missions before blahblah!