If you want to share your contacts or any other folder in Outlook you need to do the following
The person sharing their folder
Right click on the folder and select Properties
Select the "Permissions" tab and press the "Add" button
Select one or more users to share your folder with. Note you double click on the user and they end up in the field below. When ready press add.
Define the permissions for each user. You can either do this by selecting a "Permission Level" or you can specify the particular "Read", "Write", "Other" and "Delete Items" permissions
The Person Opening a Shared Folder
If you have been advised that you have been given access to someone else's folder then do the following:
From the File menu select Open and choose "Other User's Folder"
Find or enter in the user's name and choose the folder you wish to open.