To upgrade your account, first login at https://admin.metalocator.com.  Then click the user icon in the toolbar, Billing, Billing Profile as shown below

The billing profile screen will be displayed with your plan details selected:

To edit your subscription in order to change plans, or add-ons, click the Subscription Plan name (shown as Entry Level Plan above), then click Edit Subscription. From that screen you can change the plan and add any required add-ons:

Plan upgrades are pro-rated for the billing period.