Can you be more specific about what you need help with? If you need help setting up an Azure Logic App then you can find instructions on how to do that online. Please clarify what aspect(s) you're having issues with here.
If instead you need help getting attachments from DevOps then refer to the API help for getting work items here. You'll need to request the links as part of the request and then enumerate the links to get the attachments. Then for each work item you can get the attachments associated with it and download them using the API here. Logic apps can call REST APIs so all this should be straightforward.
If you need help uploading attachments to Azure Storage then please clarify what you need help with. Again, the docs are pretty clear on how it should work.