I just replied to your ticket. In short, you need to exchange some of your ETH for DAI. Or you need to buy DAI and send it to your ETH address. You can use the same wallet. Every ethereum address can accept er20 tokens. 
You can use https://1inch.exchange/#/ as a decentralized way of exchanging your ETH for DAI. Simply put the amount on the ETH you wish to exchange on the left side and select the DAI token on the right side. Approve the transaction from your metamask and you will be getting your DAI soon.
Let me know if you still don’t understand what to do. 