When you've received Lexile, you should update the website database. This page explains that process using a Google Doc template. Google Doc is not mandatory; you can follow the same procedure using any modern spreadsheet application (e.g. Excel) that can save data as CSV (comma-separated values).
Open Excel data file from Lexile.
Create a new Google Doc spreadsheet using the lexile template file (See menu item: File > Make a Copy…). The required columns are: isbn, lexile. The word_count column is optional.
Copy/paste data from Excel to the new Google Doc file.
Once complete, download the new Google Doc file as CSV to your local computer (See menu item: File > Download as > Comma Separated Values). Name the local file without spaces. For example: lexile-YYYYMMDD.csv (where YYYYMMDD represents today's date)
Ingest the local file through the web admin UI of the titleleaf site:
a. Admin > Ingestion > New
b. Type = Default
c. Attachment = lexile-YYYYMMDD.csv