After you install SharePoint for your Exchange account, only the Administrator's account is added to the SharePoint site by default. You need to add users to the site using the SharePoint interface so that other users can log in.

To add users to the SharePoint site associated with your Exchange 2010 account:

  1. Make sure that the SharePoint users are listed in CONTROL PANEL on the Users. If you need to create a SharePoint-only user (without an Exchange mailbox), click the Create Users button, fill in all the information, and make sure that all the "Services" boxes are not checked. 
  2. Log in to your SharePoint site as Administrator via CONTROL PANEL > Services > SharePoint, and click the link to access your SharePoint site. The Administrator is the user that was specified during SharePoint installation.
  3. Navigate to Site Actions > Site Permissions.
  4. Click Grant Permissions.
  5. In the Grant Permissions window, you can either add users to a previously created group, or grant them permissions directly. To add users, you can either type their email addresses into the Select Users field or click Select From Address Book and choose the users.
  6. Click the Check Names icon to make sure you entered users correctly.
  7. Give permissions to the users you have added. Read the Knowledge Base article on Permission levels and permissions for more information about SharePoint permission levels.
  8. Choose whether to send the Welcome email to new users.
  9. Click Ok to create users.

To check permissions:

  1. Navigate to a site or a library where you need to check permissions.
  2. Go to Site Actions > Site Permissions and click Check permissions.
  3. Enter the email address of a user or select them from Global Address List.
  4. Click Check Now. 

Now added users can log in to the site using the credentials you specified in CONTROL PANEL.