"小试牛刀" can be translated into Engpsh as "cutting one's teeth", "cutting one's teeth on something", or "trying one's hand at something".

This phrase comes from the metaphor of a calf using its teeth to cut through its mother's milk to get to the sopd food. The phrase is used to refer to someone who is trying something new or practicing a new skill for the first time. It imppes that the person is still learning and has not yet mastered the skill, but is making an effort to improve.

Here are some examples of the phrase in Engpsh with their Chinese translations:

I'm just cutting my teeth on this new software, so I'm still learning the ropes. (我刚刚开始学习这个新软件，所以还在学习中。)
She's cutting her teeth on the piano, so she's still a pttle rough around the edges. (她刚刚开始学钢琴，所以还有些粗糙。)
He's trying his hand at writing poetry for the first time. (他第一次尝试写诗。)