Here's a breakdown:
* 祝 (zhù) - means "to wish" or "to bless"
* 你们 (nǐ men) - means "you all" or "you guys"
* 玩 (wán) - means "to play" or "to have fun"
* 得 (de) - a particle used to connect the verb "玩" and the adjective "开心"
* 开心 (kāi xīn) - means "happy" or "joyful"
The entire phrase expresses the wish for someone to have a good time or enjoy themselves.