You should first access your Digital Dashboard. This can be done by going to "My Account", to the top right, then clicking on "My Digital Marketing".
Step 1:
Click on Upgrade in the top panel/ Compare Plans.
Step 2
The package picker will appear, select the desired plan by clicking Choose Plan.
Step 3
Choose a billing then click Continue to Payment.
Step 4
This adds the new plan to the shopping cart, click checkout then fill in your billing details.
You have now upgraded your plan!
