Step 1: Navigate to Page Layouts> Add New Post in your WordPress admin sidebar.

Step 2: Create a title, and insert your post content in the editing field.

Step 3: Add Categories from the right side.

Step 4: Add Tags from the right side.

Step 5: For a single image, click the first Featured Image Box, select an image and click the Set Featured Image button.

Step 6: Choose Layout Style for single page layout.

Step 7: Add your post excerpt.

Step 8: Once you are finished, click Publish to save the post.

Here is the screenshot that shows the various areas of the page layout post page: