How do I access "other" to free up storage space

Other contains any file that doesn't neatly fit into the other categories. There are likely user-accessible files in there (zip, dmg, pdf), cache files from streaming and browsing, system files like Time Machine snapshots, etc. You may be able to reduce some of the space by clearing your browser history, logging out/in to streaming services, backing up your system to Time Machine, or deleting files. But, for the most part such cleaning is handled by your Mac when you need space.

Rebuild the Spotlight index on your Mac

Or Force a Reindex via Terminal Command “ sudo tmutil -E / “ without Quotation Marks 

What is “Other” storage on a Mac, and how can I clean it out?

Free up storage space on your Mac

OmniDiskSweeper Safe to use

GrandPerspective 

How to delete Time Machine snapshots on your Mac

See used and available storage space on your Mac

Locate backups of your iPhone, iPad, and iPod touch

Notation - If the user is using a cloning software like Carbon Copy Cloner - suggest tweaking the Safety Net Feature in this software. It may be making additional Snap Shots that are not being Cloned to the Eternal Drive. If this should be the case, these Snap Shot could be using additional space on the drive 

The final word from Apple on Managing the " Other/ System Data “ Category

Other / System Data: Contains files that don’t fall into the categories listed here. This category primarily includes files and data used by the system, such as log files, caches, VM files, and other runtime system resources. Also included are temporary files, fonts, app support files, and plug-ins. You can't manage the contents of this category. The contents are managed by macOS, and the category varies in size depending on the current state of your Mac.

The 'Other' storage on a Mac consists of different types of files that don't fall into any particular storage category (like videos, photos, music, apps, or mail). The ‘Other’ category also includes junk files and personal files such as .pdf, .psd, .doc, browser caches, voice files, message media files stored locally, system caches, archive files like .zip and .dmg disk images, fonts, extensions, app plugins, etc. Other storage spaces on Mac is something to be taken care of since an increased 'Other' storage reduces the available free spaces on the Mac hard drive.

Hope it helps!

"Other" is managed by the system. It's cache files, system settings, etc.

It should be automatically deleted within 24 hours. Deleted files get moved to local snapshots and those snapshot are the "other" files.