No worries! This is an easy fix. From your Planner Dashboard, click on MANAGE USERS and delete them by clicking on the little trash can to the left of their name.
Next, click into their wedding, click on PLANNING PARTNERS towards the top right of your account, and then click ADD CLIENT. Assuming you’ve had a chance to prepare the wedding and release some or all tools from planner prep mode, you can click the link next to their name to send them their invitation link to join their wedding as a client. If they’ve already created their account, they’ll automatically be added to their wedding, without access to any of the other weddings in your account!
If you haven’t released any of the planning tools out of planner prep mode, you’ll want to be sure to prep and release at least a few tools, so they have something to look at the next time they log in!