Yen, Round, Circle
The combination of radicals for this kanji may not be obvious at first, but if you look carefully you'll see it. The lid is inside the head for this kanji because it's holding something in. Imagine the top of someone's head being closed by a lid. Open that lid up and peer inside... it's full of yen coins, the currency of Japan!
Another thing that will help is to associate the word round to this kanji, because it has both of these meanings. Both are right, and if you learn one that's better than not learning either, but maybe if you think about how round the coins themselves are inside this person's head, you'll remember this one too.
えん
まる
None
What does the word yen sound like? It sounds like えん. Why? because back in the day, Japanese used to have a "ye" sound, but now it doesn't. Instead, it's an "e" sound, which is why yen = えん!
Picture these round えん in your mind. Maybe look some up online too, just to be safe.