I've had a desktop computer for yonks but am new to tablets, hence what is probably a foolish query. When I receive an email with an attachment I read the email but when I try to open the attachment I am told to first download the email. How!?
What tablet do you have?
To download the whole email head to; Apps > Email > (Select the one you want) > More > Save Email as File.
To view attachmets you should just be able to select them to view once you've opened the email.