For the basic operations, you should check the according tutorial pages:
Create node
Create / move node
Connections / node configuration
Configure communication cycle
Slot / node assignment
You might also be interested in:
How to add channel B
How to change topology
You can add the second channel, channel B, through the Edit menu, if
you select two channels there:
The second channel will immediately appear
in the communication cycle and will be selectable in
the node configuration.
Disabling the second channel won't destroy your model. Channel B will then
just not be used in the simulation (and displayed differently).
How to change topology.
Good news is: you can display BUS and STAR topology and also mix them:
This can be accomplished by right-clicking the circle shaped channel designator and select the topology you want the channel to display: