Hi Taha, here is my easy 4 step plan for you.
1. Once you've logged onto Italki, click onto Learning a language which in your case is English. Look at the native speakers & feel free to email them and ask for help/advice.
2. Click onto the Resources & Knowledge sections & complete the exercises provided for you.
3.Click onto Groups & join an English Learning Group and find a language partner.
4.Keep a notepad by your computer to jot down any useful expressions that you see. Good Luck!