At the moment your coach can build plans from 4 weeks before the race to up to 19 weeks before the race.
Depending on your goal, the ideal training duration is:
14 to 18 weeks for a marathon
12 to 16 weeks for a half-marathon or a 10K
If you registered for a race which is beyond 19 weeks from now (first of all congrats!), you can start by training for a secondary goal in preparation for your main goal.
For example, if you want to do a marathon in 6 months, starting with a half-marathon plan for the next couple of month can be great to build great fitness in preparation for your marathon plan.
Don't hesitate to chat directly with Coach K from the app, and tell him more about your main goal and current fitness level, so that he can recommend the best plan for you.
Try something like: "I have a marathon in 6 months, I want a secondary goal for the next 2 months to build up for my marathon training, should I do a half-marathon plan?".
You can change your goal at any point in time in the app. Checkout this article to learn more.