Once you're in the HathiTrust Digital Library, double check to make sure you have logged in using your Cornell NetId:
Login by choosing Cornell University from the list of partner institutions, then "continue"
Journals in Hathi Trust
Once you're in the HathiTrust record, you'll need to select the correct issue. Notice that not all issues are necessarily available.
Decide which issue you want to consult, take advantage of temporary access. Then: use the check out feature to check out the entire issue. Once you've logged in and "checked out" a book or journal issue, you can read it online. It will time out after 60-minutes if you're not actively engaging with it online. You can download single pages, but not chapters or the entire book.