At the first start of the GSManager a random token will be created which can be used with !token use <TOKEN>.
To know this token you have three possilibities:
1 look into the console directly after the first start
If you have just started the GSManager for the first time, you can see the following info box:
2 Look it up in the log file
Alternatively you can take a look into the log file (logfiles/daemon.log) and search for "ADMIN TOKEN".
3 Look it up from the tokens.json
As a second alternative you can look into the file, which holds every usable token: config/storage/tokens.json
It could look like the following:
The first part is the token itself, the scond to which group you will be assgined.