Question

add a comma or semicolon if needed. otherwise, submit the text without any additional punctuation.
kimberly could spruce up her bedroom by purchasing a new headboard for her bed or making one using fabric stretched over plywood.

Explanation:

The sentence presents two alternative methods for sprucing up the bedroom: purchasing a new headboard or making one. These are two independent clauses joined by "or", but since they are part of a compound predicate (sharing the same subject "Kimberly" and the main verb idea of "could spruce up... by..."), a comma is not needed here. The existing punctuation (or lack thereof before "or") is correct as is.

Answer:

Kimberly could spruce up her bedroom by purchasing a new headboard for her bed or making one using fabric stretched over plywood.