To decorate or adorn something (to add ornaments or decorations to improve appearance, e.g., a tree or a venue).
子どもたちと一緒に教室をクリスマス用に飾り付けた。
I decorated the classroom for Christmas together with the children.
店先を華やかに飾り付けるとお客さんが増えた。
When the storefront was gorgeously decorated, more customers came.
ケーキの上を果物で飾り付けると見た目が良くなる。
If you decorate the top of the cake with fruit, it looks better.