Start small
Because you don’t have any huge exams coming up just yet, you don’t need to give yourself a big workload or stress yourself out. Try studying small bits of information at a time to introduce yourself to the process.
For example, in the evening after you finish your homework, pick a subject to try and study. Say you pick Irish, try and spend 20-30 minutes studying an irregular verb like “abair” in the past, present, and future tense. Obviously only study something you’ve covered in class, there’s no point in tackling something new by yourself.