If your five-year-old ties his shoes unassisted, your mother might call him "little Einstein." Doing something unassisted means doing it without help.
Unassisted is an example of a word with two prefixes. The first prefix, un, means the reverse of, and in this case the second prefix, a, means at. The root word sist comes from the Latin word sistere, to stand. So unassisted is another way of saying "without anyone standing by to help."