Well, one way is the Notebook entries, people will correct you and tell you what you did wrong, another is to just write people directly in English and ask them to correct you, or you can go to a website, like a gaming website or just another social website, where people speak English and learn from the other English speakers. Sorry, if I'm just stating the obvious.
By the way, when you begin a sentence, you must use a capitalized letter. Ex: A, B, C, D, E
You cannot use the word "And" at the beginning of a sentence.
You have to capitalize the letter I, if it's by itself and when it's at the beginning of a sentence. Ex: "I ran to the park, then I ran back home with icecream."
Lastly, when you want to end the sentence, you have to add a period right after the last word. No spaces in between. When you want to begin a sentence, you have to add a space and then begin writing your sentence.