You register for the summer at the following link.
The price is 4700 DKK for physical participation and covers accomodation, food and transport from/to Copenhagen Central Station and DTU Lyngby Campus. Online participation as PhD (presenting a poster, doing exercises, getting ECTS) costs 1000 DKK. Online participation without poster presentation and ECTS is 200 DKK.
PhD students which are not employed at DTU or DIKU have to register using the following link using the course number 02973 in order to get the 3 ECTS credits the school is rated for.