Please wipe out the place of the cup your lips touch by your fingers after you drink.
Please clean up the place of the cup your lips touch by your fingers after you drink.
"お茶碗に口をつけた場所を指できれいにする"
きれいにする wipe out, clean up,
お茶碗に口をつけた場所、the place of the cup your lips touch
指で by your fingers, by fingers
Please wipe out the place of the cup your lips touch by your fingers after you drink.
Please clean up the place of the cup your lips touch by your fingers after you drink.
After finishing your matcha, clean the rim of the bowl where you sipped with your fingers.
英語での表現には様々な方法がありますが、例えば以下のように言うことができます:
After finishing your matcha, clean the rim of the bowl where you sipped with your fingers.
抹茶を飲み終わったら、指で飲み口をきれいにします。
"rim" は「ふち」を意味し、お茶碗の飲み口部分を示します。"sip" は「飲む」を意味し、"where you sipped" とすることで、その場所を特定します。