To find resources on Catholic liturgy in the catalog, select the "Subject" search on the Advanced Search page. Some of the terms you would use include "Liturgy," "Divine Office," or "Rites."
Depending on your topic, you can narrow down your searching even further by adding subdivisions. You could also change the results by the format of the book, adding terms like "Encyclopedias," "Handbooks, manuals, etc.," and "Dictionaries" to the end, bringing back just those types of items.
Broadening your search could be beneficial as well, including topics like "Sacraments" and "Mass."
Here are a few examples of certain subjects available in the Library's catalog:
Handbook for Liturgical Studies by 
Liturgy in the Catechism by 
Ceremonies of the Liturgical Year by 
Ceremonies of the Modern Roman Rite by 
The Liturgy of the Hours in East and West by 
The Prayers of the New Missal: a homiletic and catechetical companion by 
Catechizing with Liturgical Symbols: twenty-five hands-on sessions for teens and adults by BV169-199- Practical Theology - Liturgy and ritual
BV800-873- Sacraments. Ordinances.
BX1970-2175- Catholic Church - Liturgy and ritual
BX2200-2292- Catholic Church - Sacraments