How to you wire a 240V air conditioning unit to a two wire supply of one hot wire and one neutral wire.

In the US or Canada, you need two hots to get 240v.

Is this a dedicated circuit? In that case you could rewire the circuit for 240v at the panel box. It's not difficult if you have a free spot to replace the single pole breaker with a double pole.

What voltage is the two wire service? And which country are you located?