This is something you should research but
An element is a set of opening and closing tags in use. Tags are labels you use to mark up the begining and end of an element . All tags have the same format: they begin with a less-than sign “<” and end with a greater-than sign “>”.
Example <p> is the starting tag of a paragraph and </p> is the closing tag of the same paragraph but <p>This is paragraph</p> is a paragraph element
Each of your radio button elements should be added within the form tag.
It just means your radio button elements should be inside the form element.
Side note: In my opinion, the message should be corrected to say, “within the formelement”, and not tag. Attributes go within the starting tag, child elements go within the parent element. But I can see this is not the only challenge where it is worded as such.