go up, climb
陞 centers on upward movement: going up or climbing. The meanings are closely related and describe physical ascent.
陞 combines the mound radical ⻖ (阜) with a right side that likely contributed the sound and the idea of rising. The exact historical development of the right component is uncertain.
The left side ⻖ suggests a hill or mound. The right side looks like a person stepping up onto a platform. Together, they show climbing up a hill.
For ショウ, imagine a show-off climbing a hill to show everyone how high they can go: show -> ショウ, and the climber goes up.