When you get your head around something, you understand it.

当你“get your head around something”的时候，意思就是你理解了这件事情。

So another idiom with a very similar meaning to that one is 'to get your head around something', which means to understand something that is challenging or confusing.

“搞清楚某件事情”，意思是理解了某件具有挑战性或者是很令人困惑的事情。