Above the NGA banner, you should see a drop-down menu saying Useful Tools. Click to see the menu, then choose 'Green Pages'. You can then (hopefully) find the seller you want to recommend.
Try clicking on 'Daylilies' or search alphabetically. Click on the seller info page, and near the bottom, you should see the options to endorse by leaving a review, or endorse without leaving a review. Either way, the seller will show up on your profile page as recommended by you.
If you don't see the seller you want to recommend, you can add their info, then endorse...
Hope this helps,
Virginia