"薰以香气" can be translated into English as "to perfume with fragrance" or, in a more concise and idiomatic way, "to infuse with aroma".
"To perfume with fragrance" directly conveys the idea of adding a pleasant smell or scent.
"To infuse with aroma" is a more natural and idiomatic expression in English, implying the act of filling something with a pleasant smell.
Both translations capture the essence of the original Chinese phrase, which refers to the act of imparting a pleasant fragrance to something.