Delegated Administration Process to accept the offer of delegated administration:
1. Open the email message from your partner and read the terms of the offer.
2. Click the link to authorize the agreement which takes you to an authorization page in Office 365.
3. Under Delegated administration, click Yes to authorize the partner to be your delegated admin.
4. If the delegated administration offer came with a trial subscription or a purchase offer, create the trial or subscription tenant account.