Microsoft Flow is a new workflow tool that enables business users to create automation to receive notifications, synchronize files, and get data between your favorite apps and services, be it on-premises or in the cloud. This is a new workflow management tool for automating workflows across applications and services by connecting web services, files, and cloud-based data. We can connect with various services like SharePoint, Office 365, OneDrive, Twitter, Facebook, Dropbox, Outlook, Instagram, Outlook, Yammer, Excel, Google Calendar, etc.

If you are new to Office 365 and SharePoint online, then check out some Office 365 SharePoint Online Tutorials.

Microsoft provides various predefined built-in templates which can be used. Just you need to sign in and use the built-in templates. You can check the pre-built templates from Microsoft Official site. Apart from these templates, you can also create your own flow. Few templates look like below:

Example on how to use Microsoft Flow in Office 365:

Here we will see how we can use "Save my email attachments to a SharePoint document library".

First, open Microsoft flow site and sign in with an email id and in the built-in templates you can see the Save my email attachments to a SharePoint document library like below:

Click on the template to use the template.

As the name suggests, whenever receiving an email with an attachment, the attachment will be saved inside a SharePoint document library.

Then we need to sign in to use the template which will appear like below:

For Office 365 Outlook, click on Sign in. Once the sign-in is successful then SharePoint Sign in is enabled. Once that sign-in is successful it will appear like below:

Click Continue.

On new email, in the choose Folder box, select Inbox like below:

Choose Site URL. Let's add our Office 365 site ID. And then in the folder path choose the MyEmailAttachements document library. 

The full screen will look like below:

From the top you can give a name and click on the Create flow button like below:

Once the workflow is created successfully, it will show like below.

Once you will click on Done to exit, it will show like below:

Now, whenever an email with attachment is received:

After this, check the SharePoint document library to see the attachment is copied into the document library like below:

You can click on My flows button to see all your workflows and then you can set it On/Off like below:

Hope this will be helpful.