You can browse play scripts by going to the 3rd floor of the library.
Browse call number PN6120 .A52.
The play scripts are organized alphabetically by the author's last name, then by title.
You can browse for scores from musical theatre by going to the call number range M1500-1527.8 on the 2nd floor of the library in the Periodicals room. You can find the Singer's Musical Theatre Anthology series in the reference collection (on the 2nd floor).
For more information on finding scores, see the guide Find Scores in the WSU Library.