Remove all books from the bookshelf and either take off the back of the bookshelf or measure the shelves using a tape measure.

Trim the fabric down to size using scissors.

Lay the bookshelf or backing down on a flat surface. Add a medium layer of Mod Podge to the back of the bookshelf and spread. Press the fabric down and smooth, working quickly. If your backing is very large, work in sections.

Smooth down using a brayer or squeegee and let dry for an hour.

Apply another coat of Mod Podge over the back of the shelves and let dry again.

If you did the entire backing, trim with scissors if necessary. Replace backer with screws or nails.