Unfortunately, the program is not very intuitive. It closely mimics the Homematic internals, which are a bit confusing. Also, at least for me the “human readable” device names are not synced between Homegear and Homematic Manager, which adds another level of complexity, as you have either to deal with the cryptic device ids or enter the names in both softwares. Homematic Manager moreover seems to allow the change names not only per-device, but also per-channel.
On the first tab (“Geräte”) you have to expand the device lines and right click on the resulting lines (=channels) and then guess if the parameter you want to change is part of “MASTER” or “VALUES” paramset (and in which channel of your device you find it at all…).
The second tab (“Verknüpfungen”) is used to link channels of devices (usually a TRANSCEIVER channel to a RECEIVER channel). Not every RECEIVER can be linked to every TRANSCEIVER, but the program will only show allowed connections. Usually this is relatively straightforward, I had troubles with a wall-mounted thermostat until I found out that here the window open notification uses an other channel than the normal thermostats.
Tell me if you need help.