For reme right now you can only buy from their website because it seems their ico is still going on: https://www.remecoin.io/
But i don't know they are accepting fiat or not. For eth, just google how to buy eth
And by the way, not the fact that they will receive investments for development, but the eth is the most common coin and you can use any large and demand exchange.But i don't know they are accepting fiat or not. For eth, just google how to buy eth