Updated June 4, 2021
Step 1: Create a new Google Sheet (spreadsheet)

Step 2: Structure your data in following columns

Column A: Text of the post
Column B: Link URL (optional)
Column C: Comma separated image URLs (optional)

There should be no header row.
The image below shows a .CSV; the formatting is identical:



Step 3: Find the spreadsheet in RiteBoost Bulk Creator by its name when you create New Formula