Based on the level of respect or formality, you can say "How can I address you?" in Korean in 3 ways:

• Informal: nae-ga neo-reul eoddeokke bulreoya hae? (내가 너를 어떻게 불러야 해?) - nae-ga neo-reul can be omitted
• Formal: je-ga dangsin-eul eoddeokke bulreoya hanayo? (제가 당신을 어떻게 불러야 하나요?), je-ga dangsin-eul eoddeokke bulreoya hapnigga? (제가 당신을 어떻게 불러야 합니까?) - jega dangsin-eul can be omitted
• Very Formal: je-ga dangsin-eul eoddeokke bulreo deurilkkayo? (제가 당신을 어떻게 불러 드릴까요?), je-ga dangsin-eul eoddeokke bulreo deuryeoya halggayo? (제가 당신을 어떻게 불러 드려야 할까요?) - jega dangsin-eul can be omitted

- how: eotteo-ke (어떻게)
- I: nae-ga (내가), je-ga (제가)
- to address: bureuda (부르다), jeopgeun hada (접근하다)
- you (objective): neo-reul (너를), dangsin-eul (당신을)

Please refer to How to pronounce Korean Alphabet for the English pronunciation in this answer.