Windows Phone 8 Basics - Share things on my phone - To open a SharePoint site for the first time on your phone

In the App list, tap Office Office icon.
Flick to Places, and then tap New New place icon.
If you already signed in on your phone with a Microsoft Exchange or Microsoft Office 365 account that includes SharePoint Online, your SharePoint team site may already appear in Places. Just tap the team site to open it. For more info about setting up email accounts on your phone, see Set up or delete an email account.

Type the address for a SharePoint site, document library, or folder, and then tap Go Go icon on the keyboard. Make sure you include http:// or https:// at the beginning of the address.

If you have an Exchange email account set up on your phone, SharePoint will try to use that user name and password information to sign in to the SharePoint site. If you don't have one set up on your phone, you'll be prompted to enter your user name and password.

If you're prompted to sign in, do one of the following:
If the Microsoft Office 365 sign-in page appears, type your user ID in the corresponding box, type your password in the Password box, and then tap Sign in.
If the Site screen displays with boxes labeled Email address and Password, type the email address and password for your Office 365 account in the corresponding boxes, and then tap Done.

If the Site screen displays with boxes labeled User name, Password, and Domain, type your user name, password, and the domain for your account in the corresponding boxes. (For example, if you log on as "contoso\kevinc" at work, you'd type contoso for the domain name and kevinc for your user name.) Tap Done.