The sentence structure used is fine. كيف ظهرت هنا؟ However, the word ظهرت = "appeared", is uncommon. جئت = "came" would be a more common for of expression. In The Gulf Area, people would colloquially say كيف جيت هنا or شلون جيت هنا. in Egypt, the sound of the letter ج would be pronounced as "g" in gate. it would be جيت هنا ازاي؟ ازاي = "How" in Egyptian. In Fus-ha Arabic, it would be, كيف أتيت (إلى) هنا؟

كيف وصلت هنا ؟ ، كيف جئت هنا ؟