Ahhh, I remember my first day of CNA clinicals like it was yesterday. I had a resident ask me to help them to the BSC. I got gloves, pulled out the BSC, and the world titled on it's axis because I had the epiphany that "I literally just introduced myself to this human being, and I'm about to stand here while they defecate and then wipe their butt for them. I will then take the bucket of feces, inspect it, and flush it myself".
Healthcare is bizzare, man!
Things become common as you gain experience, but the fact of the matter is, when you've never been exposed to something it's perfectly acceptable to have no idea what to do - tubes and containers putting stuff in, taking stuff out, measurement devices, charting systems....it's a lot to learn!
Ah, I could give you a list of all the stupid things I've done as a CNA/ nursing student / nurse, but it would be a loooong list. Have yourself a chuckle at this experience, learn from it, and forgive yourself. In the future, if you're not sure how to empty or change a device, just ask.