WCF REST Service - "POST" Method not allowed

Am developing a wcf rest service , I was able to do GET operations ,
but "POST,DELETE,PUT" prompts me with method not allowed.
Below is my code.
-------------------
 [DataContract]
    public class People
    {
        [DataMember]
        public int PeopleID { get; set; }

        [DataMember]
        public string FirstName { get; set; }

        [DataMember]
        public string LastName { get; set; }

        [DataMember]
        public string Address { get; set; }
    }

Interface:
------------
 [OperationContract] Go to the complete details ...