Step 1: Go to the list or library for which you want to delete a previous version.
Step 2: If the name of your list or library does not appear, in the left nav, select Site contents, and then select the name of your list or library.
Step 3: Right click on the space between the item or document name and date, and from the menu, select Version History. To see Version History, you may need to scroll the menu.
Step 4: In the Version History dialog, hover next to the version you want, and to get a list of options, on the right side, select the down arrow. Select Delete.
Step 5: To delete the version, select OK.