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: