In Illustrator, you can enable guides by going to the View menu and selecting Guides. You can also access guides by pressing the G key.
When you enable guides, you can create horizontal and vertical guides by clicking the Horizontal and Vertical buttons, respectively. You can also create guides based on screen size and orientation by clicking the Guidelines button.
To edit a guide, double-click the guide that you want to edit. To delete a guide, select it and press the Delete key.