That depends on which benefit your employer offers: BFNL or Alleo.
For BFNL:
Go to MijnFitnessplan and log in using your employer's company code. Don't know the code, or not sure whether your employer participates? Complete the employer check. Then follow the steps to choose the subscription that suits you.
For Epassi App:
Request a subscription in the Epassi app, without a company code. Log in via the Epassi app or go to app.epassi.nl.