If you're already on EE with a Pay Monthly mobile contract, you can't as they aren't Upgrade deals.
They are deals for Plusnet customers thinking of joining EE as a new mobile customer.
If you're not an existing EE Customer, then you can just choose the plan you like through your Plusnet account, and you will need a PAC Code from your old network. The instructions can be found here: https://ee.co.uk/help/mobile/getting-started/keep-my-number/transfer-my-number-to-ee
