I would like to associate a different Youtube channel with single adsense account

Now You can earn money by uploading video on YouTube.For doing that you need your own one YouTube channel.and some uploaded good videos.If you don't have then sign up for YouTube first and upload some unique video like any How to trick or your own creation.

Please Note that do not upload any video which is already exist on YouTube.It will cause permanent suspension of your account.

Please read carefully Some FAQ about Video Eligibility:

Which videos are not eligible?
Your video is not eligible if it contains content that you didn't create or get permission from its creator to use. You need to be able to show written permission for the following video elements:
Audio: copyrighted sound recordings, live performances, background music, etc.
Visuals: images, logos, software, video game footage, etc.
Any other content you don't own worldwide commercial usage rights to.
Examples of videos that are NOT eligibleYour video contains a song you purchased for personal use (e.g., bought on iTunes or in a store) but didn't obtain a commercial license.
You found a video on the Internet and you cannot prove that it's in the public domain.
You are singing words of your favorite copyrighted song and there is copyrighted audio in the background, such as instrumental or karaoke tracks.
You have used content from someone else without permission, but you haven't yet received a copyright notice on your video.
Your video does not provide proper attribution or credits as required by a license.
If your video is not eligible, it may be removed from YouTube.

Now up to this still you can not earn money for your video.You need some further steps.First you need to Enable Monetization.Go to Channel setting >>Features >>Monetization. Now click on Enable.After doing this go to Video manager>>Uploads >>Select any video>>Then click on Monetize.Then your video may under review and after some time it will fully approve for make money.

Now for in order to receive money you need your own adsense account. And then associate it with your channel.

If you already have an approved AdSense account:

Access the Monetization page in your Channel Settings.
From the AdSense Association page, you will be directed to AdSense.
Select the option at the bottom of the page to choose the Google Account you wish to use.
Enter the password for your Google Account.
Accept the association and you will then be redirected back to YouTube

If you have never created an AdSense account before:

Access the Monetization page in your Channel Settings.
From the AdSense Association page, you will be directed to AdSense.
Select the option at the bottom of the page to choose the Google Account you wish to use.
Enter the password for your Google Account.
Confirm the association and provide your billing information before submitting.
You will then be redirected back to YouTube. (Note: AdSense may email you an update.)

How to associate a different or Multiple Youtube channel with single adsense account:

If you have created more than one youtube channel or you want to monetize your friend's channel than it is possible to do it without heaving multiple adsense account.Just follow the steps given below.

Step 1:

Go to>>Video manager>>Uploads