You can use normals in a 3D model without a tablet by using 3D software (e.g., Blender, Maya, 3ds Max) with mouse-and-keyboard controls for editing or previewing.
Normals define a surface’s direction (critical for lighting and textures); most software lets you adjust them via menu options (like Blender’s “Recalculate Normals”), sliders, or shortcuts—no tablet needed. For example, in Blender, toggle normal visibility (Viewport Overlays > Normals) or fix flipped normals with Ctrl+N using just a mouse and keyboard.
If you’re new, start with Blender’s free built-in tools—they work well without extra hardware.