Calling Asynchronous method from a Synchronous method  

In our application we are forced to call an Asynchronous method from a Synchronous method. The reason is that we are using a 3rd party package that only provides async methods in certain cases.

My understanding is that this is possible. Two questions:

1. What is the best way to implement this? And, more importantly
2. How do I ensure it is safe? -- I read somewhere that doing this can lead to deadlocks.