STEP 1: Login to ThemeForest.
STEP 2: Go to Downloads page.
STEP 3: Click Download button next to ListingPro, and select License certificate & purchase code.
STEP 4: Open the license.txt or license.pdf file and copy the Item Purchase Code.
STEP 5: Go to WordPress Dashboard, and insert the Item Purchase Key, and click Activate
Next, a following text Valid License Key should appear and the activation box disappears after refreshing the page.