Digital magazine downloads are handled in different ways, depending on where you get them. Earlier versions of the iOS software included a feature called Newsstand that collected issues from most digital subscriptions in one place, but Apple discontinued it in 2015 in favor of Apple News.
Some sites may offers copies as PDF files you can open in a web browser and save to the iBooks app (or the specific app you use to handle PDF files, like Adobe Reader). Some publications have stand-alone apps that store electronic issues within their own internal libraries. Digital publishers may also direct you to online folders or servers.
If you’re not sure, go back to the site where you signed up for the digital magazine and check its support area or frequently-asked-questions page.
If you subscribed to the magazine through the App Store app on your iPad, the downloaded issues are most likely contained within a separate app of the same name — and not in the iPad’s iBooks library. (The Google Play store for Android has similar magazine apps.)
Electronic bookstores like Amazon and Barnes & Noble also sell digital magazines, so you may find subscription downloads in the purchased content of the Amazon Kindle app or Barnes & Noble Nook app. Likewise, digital newsstand apps like Texture and Zinio file your downloads within the app you used to buy the subscription.
The internet has several magazine-collection sites that offer free downloads of PDF periodicals or request payment to the site itself and not the magazine’s publisher. These types of sites often let you download a large PDF file in the tablet’s browser and then save the file to a designated PDF-viewer app. (Some of these sites are in legally gray areas, so be careful about where you share your credit-card information. When in doubt, go to the publisher’s website.)
If you like to read digitized copies of printed magazines, your local library may have a collection to read in its electronic collection that you use with the RB Digital app for iPad and your library card, so check with your local branch. The Internet Archive also has a free digital magazine collection to browse.