Below is a list of steps to insert a line numbering in a document:

1. Check if line numbering feature is currently enabled. If so, click on the 'Disable' or 'Turn Off' button given in the menu.
2. Navigate to 'Page Layout' and then click on the 'Line Numbers' option from the menu.
3. Choose the 'Add Line Numbering' option from the menu.
4. Choose the numbering style from the menu. For example, 'Continuous' number on the left margin.
5. Now click on the 'Set Line Numbering Value' option from the menu and alter the count as per requirement.
6. Finally, click the 'OK' button to save the line numbering settings.