How to create a Mirror in Blender

Step 1: Open Blender and delete the default cube. Go to the "Add" menu and select "Plane". This will create a flat plane in the center of the workspace.

Step 2: In the "Object Mode", select the plane and press "Tab" to enter "Edit Mode". Use the "Scale" tool to adjust the size of the plane to match the size of the mirror you want to create.

Step 3: Use the "Grab" tool to position the plane to be parallel to the ground plane, this will create a mirror that reflect the scene.

Step 4: Go to the "Material" window and add a new material to the plane. Change the color of the material to match the color of a mirror, usually a silver color.

Step 5: In the material settings, under the "Surface" tab, select "Glass BSDF" and set the "IOR" to 1.5. This will create a transparent material that will reflect the scene.

Step 6: Create a new light source in the scene to illuminate the mirror.

Step 7: Use the "Camera" tool to set up a good shot of the mirror.

Step 8: Use the "Render" option to create a final image of the mirror.

Step 9: (Optional): To make the mirror more realistic, you can add a glossy reflection to the mirror by going to the "Material" window and under the "Specular" tab, increase the "Roughness" value.

Note: This is a basic steps on how to create a mirror in blender, you can always add more details and adjust the final outcome as you like. Also, you can add a background image to the scene, and the mirror will reflect it.