get the hang of 掌握窍门；掌握…的窍门；熟悉…的门道

【例句】
It's a bit tricky at first till you get the hang of it.
刚开始有点儿难，掌握窍门后就好了。

It may seem difficult at first, but you'll get the hang of it after a few weeks.
这事儿初看不容易，可是过几个星期你就能摸着门儿了。