To take a screen shot with a Samsung Galaxy tab is slightly different from the normal Samsung smartphone which is press the power button and the home key at the same time.
For the Samsung Galaxy tab
Hold the back button number 2 and press the power button number 1
at the same time

To view your screen capture
Go to My files
Scroll down to the folder ScreenCapture
Your screen capture files with be here in a list view
To delete a Screen capture
Go to My files
Scroll down to the folder ScreenCapture
Select the image from the list
Select Menu
Select Delete
Confirm deletions
Your image will be deleted
Share a screen capture image
If you want to forward a screen capture to an email contact or to any of the social networking apps you have installed
Go to My files
Scroll down to the folder ScreenCapture
Select the image from the list
Select Menu
Select Share
Select either your email client or social network you want to send it to.
A new window will open for your to either add an email contact or write a comment for your status post to your social network