Microsoft has bundles a Modern-styled app called Mail along with Windows 8.
So, you need not separately install an e-mail client. Mail app does the job just fine by acting as your default mail client.
In order to get Mail app working, you need to add one or more mail accounts to it.
If the credentials are authenticated successfully, then Mail app fetches the mail folders of your account, as well as mails from some past days.
After you have set up mail account(s), you can write a mail in two ways.
In this page,
Click on the send button to send the mail. You may also save it in drafts if you want to send it later. Click on the button marked with “X” to save in drafts, or delete the mail.
If you want to mail a document, you can do it directly from Windows Explorer.
Right-click the file > Send to > Mail Recipient
Either of the ways will launch the new mail composer windows of the default mail client, which is Mail app in this case. The new mail will already have the document attached.