After selecting Cohort in Visualization Type, you get to control two tabs: Columns and Options.

In the Columns tab, you select the Bucket column (data-based), the Stage column (defines the different stages for your cohort), the Bucket Population Size (column that has the total size of the initial Bucket), and the Stage Value (the column that has the value for cohort stages):

In the Options tab, you can select Time Interval (Daily/Monthly cohorts) and an option to fill the empty values with zeros if need be: