There is no standard process for this, only recommendations: it is a good practice to start planning as early as possible until it is clear to everybody that a plan is not a commitment.
If I were you, I would follow the 1/3 rule: plan the first 1/3 very detailed on the task level, plan the second 1/3 on the user story level, and finally plan the last 1/3 on the epic level.
With this approach you can have an idea when you might finished the project, and what are your next steps. With this information you can go to your boss or supervisor and see whether this is fine with him or her and talk about risks. If you can do this before the start you can eliminate problems before even officially starting the project.
After a several days or weeks, you do you planning again using the information from the past days/weeks, but this time user stories might become tasks, and epics might become user stories etc.