Lot's of people getting confused (including me at first) about how to actually deposit XMR on Dream.
First of all to actaive your XMR wallet on Dream put '/xmrWalletService' at the end of the Dream URL.
Dream, slightly confusingly, gives you a payment ID on your wallet page. You do not need to / aren't able to include this as a payment ID when you send from your GUI wallet which is causing a lot of people confusion when they try and send money from the GUI because it'll tell you it's not a valid payment ID.
Don't worry about it.
Dream XMR wallets use integrated address's so the payment ID is part of the wallet address. Basically you can just send the XMR from your wallet to the Dream address and leave the payment ID blank.
When you see it in your transaction history it will have the payment ID given by Dream in the payment ID line automatically.
As always follow good OPSEC when using XMR. Run a full node or use a VPN when using a remote node and never send directly from an exchange.
Here's my XMR FAQ for further reading
Interesting, I'm familiar with the whole integrated vs payment ID but I see one listed. They and other monero sites really need to add a little note explaining the two types of integrated addresses and the non-integrated w/ payment id approach.