To access reports, click on Reports in the left side menu:
Select the report type you want to convert from by using the dropdown menu in the upper left corner, and use the date filtering options to find the report. Usually users have a type called Offer they convert reports from:
Converting the report
Click the three dots in the rightmost column for the report, and select Convert:
You will now see a form where you can select the desired Type and Activity and click Add report: