I am assuming that just like me, your tokens or coins can be under the Ethereum network since they are in MEW. Now, the best thing to do, of course, is to add ETH to your wallet. And you can buy it from exchanges we have around. I am not sure if MEW is already allowing its users to buy ETH directly from them but that would be great option if it is provided. MEW used to be a very popular wallet service provider but they stop innovating so it is not anymore that used often by many even by those in Ethereum network.