Thank you for taking the time to read this blog post, I wrote this as I was trying to find a good blog post to point some work colleagues. I was not successful so instead, I am writing this post.
Permissions & Licenses
To ensure you can successfully access the Office 365 Adoption dashboard you need two things.
First off you need the Power Bi license to access the portal
The minimum required is Power BI (Free)

once you have the license, now you need the permission
the minimum permission is “Reports reader”

Ask your Admin to assign the license and reader permission
Dashboard setup
Now that you have the free PowerBI dashboard and the “Reports reader” its time to set up the dashboard! You will also need your Office 365 TenantID (Ask your Admin)
To start the setup go to https://powerbi.microsoft.com/ and sign in
Once you log in you will see a screen that looks like this

So now we need to add the dashboard,
First, click Apps

Then Get apps

Now click Apps(again)

Now in the search box type “Microsoft 365” (Yes Microsoft, not Office – this changed in September 2019) and click on “Get it now”

Once PowerBi has installed the dashboard for you its time to add the tenant id (then click Next)

Next, you will need to select the Authentication method (check with your Admin, FYI every time I have set this up it has been to select OAuth2) Then Click “Sign in”

Follow the bouncing ball to authenticate into the tenant

Congratulations you did it! – Click the dashboard and start looking at your data
Please note if you launch the dashboard straight away it may take a few minutes to display the data (be patient)