Immerse yourself in it.
The best way to learn English, or any language for that matter, is to immerse yourself in it.
How you can go about doing that depends on your current level. If you're new to English, I would suggest starting with cartoons and animations.
In addition to this, music, movies, and books are amazing learning tools as well!
Basically, whatever you can listen to or read on a daily basis will help you a lot.
In this day and age, the internet is practically bursting with videos aimed at helping people with grammar, vocabulary, and pronunciation, so hop on YouTube every chance you get and check them out!
There are a lot of apps and games out there that can help you with mastering the English language. So, if you have access to an internet connection, you practically have an unlimited resource to help you with your English journey.
Last but not least, give it time and don't lose your patience! English is a very complex language with an enormous vocabulary, so get comfortable with the idea that you have to put in time and effort to master it. But it'll be worth it, that you can be sure of! :)