Hi Jordy, I think that's a slight hickup in the course. For making connections betweens entities you need a 'reference selector’.
Drag that on your page and it will work. Do mind that the reference selector has two options for displayy. One as the here described ‘drop down’, the other as a ‘select page’. Hence the mixup in the learning path I guess.
The regular dropdown is suitable for enumerations (preferable with more than 5 options).