if(d=="Vayush" && e=="Vasireddy")
is comparing pointers to string literals, thats wrong because you want to compare contents and not addresses. The compiler is telling you to use the standard function strncmp instead of ==, in this case strcmp can do the job:
#include <stdio.h>
#include <string.h> // strcmp
int main(void) // Use a valid signature
{
    // Use meaningful names for your vars
    char usr[10];
    char pwd[10];
    // Do not use goto, loop until you get valid values
    while (1)
    {
        printf("Username of the agent: ");
        // scanf return the number of input items successfully matched or EOF
        int n = scanf("%9s", usr); // %9s in order to avoid buffer overflows
        if (n == EOF) { break; }
        if (n == 1)
        {
            printf("Password: ");
            n = scanf("%9s", pwd);
            if (n == EOF) { break; }
            if ((n == 1) &&
                (strcmp(usr, "Vayush") == 0) &&
                (strcmp(pwd, "Vasireddy") == 0))
            {
                break;
            }
        }
        printf("wrong username and password\n");
    }
}