can't help doing:
When I heard the news, I can't help crying.
I can't help finishing watching the movie in one sitting.
Coco can't help answering the question because she's always kind-hearted.
When she heard the joke, she can't help laughing.
can't help doing sth意思是情不自禁做某事，只要有合适的场景，发挥你的想象，加上一个主语，换上合适的动词套进去句子不怕造不出来，加油，相信自己。
help oneself to sth 随便吃或喝。。
In China, it is usual to help oneself to the food placed at the center of the table.
中国人的习惯就是各人从餐桌中央菜盘子里夹菜。（摘自有道，有改动。）
Tim, help yourself to some fruits.
这个搭配用的时候一般情况下可以省略掉to及以后的内容，只说help oneself即可。
希望帮到您！
追问可惜晚了一步，但十分感谢！！！
追答嗯 呵呵 我打字慢了些 以后我尽量快一点 追问的感谢很贴心 thanks a million.开心哟