You can view VLANs using the sh vlan-switch brief command.
The developers have made this a lot easier for us because they've created macros.
So VL displays the VLANs such as the following.
this command allows us to add a vlan
notice we need to be in configure mode so configure VA 3
and you can see a macro has been run
so do sh vlan or sh vlan-switch
shows me that, that vlan has been added
I could also just do VL which shows something similar,
so the developers have made it easier
by allowing you to pre-create an EtherSwitch module
but be aware this is still just a Cisco router with an EtherSwitch module inserted.
So you can do it either the hard way as I demonstrated
or use some of the pre-built options available within GNS3.