To clear your iPhone's "Other" storage, delete Safari's cache and set your messages to auto-delete. You can also offload large apps or delete and reinstall apps with big caches. Deleting emails with large attachments and clearing the Mail app's cache can help, too.

You can either go to each folder (that contributes to the Other storage) on your system and selectively delete the files from there or use a third-party Mac cleaning utility to handle it for you.