To follow lots, log in at https://www.troostwijkauctions.com/. Once you are logged in, you can view the relevant auction and lots. At the top right of the photos on the lot page, you will see a 'heart' icon. By clicking on this, you can follow this lot.
If you no longer want to follow a lot, click on the 'heart' icon. If you click on Account -> Favorites at the top of the screen, you will find all the lots you have selected to follow. There you can also unfollow the lot(s).