Adding Erc-20 Token

I want to know if I can add erc-20 token in the exchange.

You can add any coin in your exchange. For blockchain connection however you need to have your ERC20 coin added into bitHolla Vault. bitHolla charges for adding new tokens and you better contact sales@bitholla.com for that matter.

You can add pairs and coins, just need to apply for listing on bitHolla.