These four locations are all in Uttarakhand. Haridwar will serve as a base for visiting all four of these locations. Haridwar is well connected to Delhi and can be reached by bus or private taxi.
Since Haridwar is in the plane zone, a direct train is also available. If you’re traveling by flight, Dehradun is the closest airport. Many travel companies in Delhi sell dedicated Chardham Yatra Tour packages.