This pattern is used to say that someone is not good at a particular action or activity. It's a straightforward way to describe lack of skill, similar to saying 'I'm bad at (doing) ...' in English. The の nominalizes the verb phrase, turning the action into a noun phrase that can be the subject of 下手.

It's a common, everyday pattern used in conversation. You can use it to talk about your own weaknesses or to comment on someone else's. Because it is a simple N5 pattern, it's safe to use in most situations, though it is a bit direct—if you want to be softer, you might say あまり上手ではありません, but for N5, this is fine.

Note that 下手 (heta) is used for lack of skill, while 上手 (jouzu) is for being good at something. The structure is the same: verb-dictionary form + のが上手.