You can select multiple items by long press on a single item/row and then just taping other items you want to edit and assign them to a category.
After selecting items tap on the 'edit' icon at top and you will be presented with list of categories. You need to tap on the desired category and then need then just tap on the 'tick' icon at top to complete the process.
Deleting selected items:
After selecting items tap on the 'delete' icon at top and you will be asked for confirmation. Please tap 'ok' to delete the selected items.