I am not familiar with photoage.com, but you can create A-Records easily via the panel.
To achieve the result in the example, you would do something like the following, assuming example-domain.com has already been added to the DreamHost hosting system.
Firstly, [color=#CC0000]Do NOT add blog.example-domain.com to the DreamHost system.[/color]
Go to Domains -> Manage Domains in the panel and click the small DNS link next to example-domain.com
Now, in the section Add a DNS record to example-domain.com. fill in the following fields.
Click the Add Record Now! button and you are done.
Note, it will take a little time for the new A-Record to become active. This can vary from a few minutes to a few hours, be patient.
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