First thing you must install TFS SDK, you can download the Team Foundation Server SDK from the below link.
http://www.microsoft.com/downloads/details.aspx?FamilyID=7e0fdd66-698a-4e6a-b373-bd0642847ab7&DisplayLang=en
Steps:
1- Create windows or web Application
2- Add References for :
Microsoft.TeamFoundation.Client
Microsoft.TeamFoundation.WorkItemTracking.Client
3- The below code will help you to work with Team Foundation Server
using Microsoft.TeamFoundation.Client;
using Microsoft.TeamFoundation.WorkItemTracking.Client;
// declaration variable
private NetworkCredential networkCredential = new NetworkCredential("enter here User Name", "enter here password", "enter here domian");
private Uri uri = new Uri("enter here TFS URL");
string projectName="enter here TFS prject name";
string worktemType = "enter here Work Item Type";
// Set Authentication To TFS
TeamFoundationServer teamFoundationServer = new TeamFoundationServer(uri.AbsoluteUri, networkCredential);
teamFoundationServer.Authenticate();
//Add Work Item
WorkItemStore wis = (WorkItemStore)teamFoundationServer.GetService(typeof(WorkItemStore));
Project tfsProject = wis.Projects[projectName];
WorkItemType wiType = tfsProject.WorkItemTypes[workItemType];
WorkItem workItem = new WorkItem(wiType);
workItem.Title = "Test Work Item";
workItem.Description = "Work Item Description";
workItem.Save();