Most people don't use dosers for kalk, you simply just add it to your ato water and it'll add kalk to your system. You can use dosers to add alkalinity and calcium separately into the tank.
You use a kalk reactor in conjunction with an ato. You connect the output hose from the ato to the reactor. When the ato kicks on, it'll force water into the reactor and itll push saturated kalk into the tank. I don't want to be too long winded but I can go into further detail if you want.