You will get an email from GoCorp after your company admin has registered you to GoCorp. Click the "Try GoCorp" at the bottom of the email and it will take you directly to the Gojek App. 

Please sign up if you have not yet registered to Gojek, but if you have a Gojek account, then your GoCorp account will be automatically activated. Make sure you choose "GoCorp" as the payment method for your next business trip.