Sentence examples for the first installment from inspiring English sources

"the first installment" is a correct and usable phrase in written English.
It can be used in a variety of contexts, but it is often used when referring to a series of payments or a multi-part project or process. Example: "I just finished reading the first installment of the new book series and I can't wait for the next one to come out." Example: "The first installment of the loan is due at the end of the month." Example: "After completing the first installment of the project, we will move on to the next phase."