Registration Run-Down w/ Images! (A comprehensive run-down of the registration process) &
Part 2
To expand on this, it looks like Princess 2025 registration is tomorrow. So you'll go to this page to find the links to register tomorrow morning.
https://www.rundisney.com/events/disneyworld/disney-princess-half-marathon-weekend/
If you follow the Princess 2025 thread, you'll see when other DIS members are able to start filling the queue tomorrow morning (usually about 15 min before registration begins at 10:00am eastern). Additionally, if other DIS members get through registration and have extra queues that have short wait times, then they can DM you the link to help get you in as well.
https://www.disboards.com/threads/princess-half-marathon-weekend-2025-feb-20-24-2025.3941285/
To maximize your chances to get registered, the common advice is multiple browsers on multiple devices. Each browser on each device is a single queue entry that gets randomly assigned a place in line at 10:00am eastern (if on time registration opening). So a Chrome on an iPad, laptop, and iPhone are three different queues with three different chances at a low wait time. While a Chrome on a laptop, and a second tab of chrome on the same laptop is the same queue entry and only gets you one unique chance at registration. Plenty of other tips in the first linked thread, but the queue thing is the #1 tip.