I understand you probably won't have a lot of time. Language learning requires motivation (which you got!), dedication and consistence. (repeat, repeat and more repeating). The best advice I can give you is to study the language everyday, for 30 maybe even 60 minutes if you are able to. If you manage to do something every day it will stick better and develop a better long-term memory (of whatever you are learning). If, for example, you only have time during the weekends, that's okay too! Use your time well in the weekends, then try to repeat the learned vocabulary on the way to school (in the bus/train). Even 10 minutes would be sufficient. Manage your time well, repeat, use different sources. You're bound to be successful. :) Best of luck!