There are different types of knots that you can choose from. The choice depends on the person's style, the ties' size, the occasion and the shirt being worn. You can find some written instructions with lots of clear pictures as well as some clear videos on how to tie a tie that you can easily follow. I will share with you a few websites and videos that I believe you will greatly benefit from if you need help with this particular skill.
Some sites for written (and pictured) instructions that you can check out are:
For videos on how to tie a tie, you can visit:
Also, youtube.com has a lot of videos available.
Here is one video recorded example for you: