You can start running a bulk edit in two ways. First, you can click the three dot menu at the top of your Table, and select "Bulk Edit Items" from the dropdown. This will bulk edit every item in your items table view by default.
Second, you can check the boxes next to individual items and click "Bulk Edit" from the Menu at the bottom of the page to have the option to apply to bulk edit to "All Selected Items" or "All Items Matching Filters".
To learn more about what filters you can add to an Items Table, read the article below:
NOTE: Bulk Edits can only be made on up to 5,000 items. If your number exceeds that amount, try adding filters to your table to lessen the amount of items in the bulk edit.
Once you've added your edits, Click "Apply" in the upper right hand corner of the bulk edit pop-up.
Bulk edits are permanent. There is no "undo" button. This means that it is up to you to find the items you bulk edited and filter in reverse to get your items to how they were before.