Importacular does have security settings built into it. The security group of the first person who activates Importacular gets all the rights and, apart from Raiser's Edge supervisor users, nobody else has any rights. If somebody activated Importacular who is in a different security group to you and you are not a supervisor users then all of the menu items and buttons will be disabled.
The person who activated or a supervisor user will need to assign security to those people who will be using Importacular before you are able to use it.
For more information see the security chapter in the user guide here.
Update:
There does appear to be a bug in the application where the system is set up without going into the security settings at all. Aside from the above solution it is also possible that other supervisor users may be locked out too. The workaround is to setup any security option, save them and then, if not actually required, they can then be removed. This will allow other supervisors access. See further information on setting up security groups here.
If you are a supervisor user but experiencing these issues then please log in as the Supervisor user instead and follow the instructions above.
We hope to address this issue in a future patch.