It is very easy to become affiliate but very difficult to sell. Please guide me as to how to selling being affiliate.

Yes becoming affiliate is easy but how to make it as an affiliate isn't easy. I think you mean how to promote your affiliate products/service, as selling has to be done by the merchant itself.

1.To promote your affiliate products you need to get ad seize that suit your website and place them on your website.

2. You can create a page on your website dedicated to your affiliate product and optimize the page for search engine.

3. Put your affiliate link in your Cokoye signature (with short url)

4. You can run Cokoye ads for it if you desire see Cokoye ad rate here http://cokoye.com/general-chats-room-forums/cokoye-advert-rate-how-to-advertise-in-cokoye

5. Be active and run Cokoye forum marketing see detail on how to run Cokoye forum marketing http://cokoye.com/internet-marketing-discussions/cokoye-step-by-step-forum-marketing-guide

6.Put the affiliate link on your emails you send out.