Sign into your account. This will take you here:

At the top of the page, select Projects. This will take you here:

Within the All Projects box, select the orange button titled Inactive Projects.
Then, select the project that you wish to activate. This will take you here:

Within the box titled ‘Project’, select the orange button titled ‘Edit’ in the top right corner. Your page will look like this:

Next to the box titled ‘Status’, select ‘Not Enabled’. A drop down will appear. Select the option that says ‘Enabled’.
Then, select the green box titled ‘Save Updates’.