Right now, there's no way to switch directly from a regular Splice subscription to a Create Pro plan. If you'd like to switch, you'll need to cancel your current plan and wait until the current billing period ends, at which point you can resubscribe to the Create Pro plan.
If you're looking to switch plans immediately, please contact our support team using the blue chat widget-- we can assist with fully cancelling your current plan so you can resubscribe to Create Pro right away.