Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello,
Since you purchased via GoDaddy, the regular Microsoft instruction won't apply to you. Admin Center is only if you purchased directly from Microsoft. Your support is actually also via GoDaddy.
GoDaddy follows their own instruction, even though their backend is all Microsoft's products, their interface and access point can be different.
This is their instruction: https://www.godaddy.com/help/add-microsoft-365-user-email-accounts-8900
As for Excel log in issue, check with GoDaddy the exact type of license or subscription you have. You may not have the correct subscription that includes Excel /Office apps.