If a token doesn't show up in MyEtherWallet, you'll need to add custom token information.
In MyEtherWallet click the "Add Custom Token" button and fill in the fields.
Example for adding Blockchain Index (BLX):
- Address: 0xE5a7c12972f3bbFe70ed29521C8949b8Af6a0970
- Token Symbol: you are free to write anything here (without spaces or special characters), but the token symbol must be available/not already taken. For example, you can write BlockchainIndexBLX, CCBLX, DAABLX, JohnDoeBLX, etc.
- Decimals: 18