Under this project's constraints, I can't use CAPICOM.  
So, yes, I could use CertAddCertificateContextToStore(),
but that requires a context, which I would need to use
then CertCreateCertificateContext, which takes me back to
my original posting.  I need help with
CertCreateCertificateContext in C# (MSDN examples are in
C++).  Here is some of the code I am currently using:

// DllImport declaration
[DllImport("crypt32.dll", SetLastError=true)]
public static extern IntPtr CertCreateCertificateContext(
            int dwCertEncodingType,
            IntPtr pbCertEncoded,
            int cbCertEncoded);

// at this point, the "My" store is already opened
// read certificate
string fileName = @"C:\TestCert.pfx";
FileInfo fileinfo = new FileInfo(fileName);
BinaryReader br = new BinaryReader(fileinfo.OpenRead());
byte[] Bytes = new byte[fileinfo.Length];
br.Read(Bytes,0,(int)fileinfo.Length);
br.Close();

// We need to marshal the byte array Bytes into a pointer
IntPtr buffer = Marshal.AllocHGlobal(Bytes.Length);
Marshal.Copy(Bytes,0,buffer,Bytes.Length);

hCertCntxt = CertCreateCertificateContext
(X509_ASN_ENCODING, buffer, Bytes.Length);

if(hCertCntxt.ToInt32() != 0)
{
    System.Windows.Forms.MessageBox.Show("got
context");
}
else
{
    int iErrorCode = Marshal.GetLastWin32Error();   
    Win32Exception ex = new Win32Exception
(iErrorCode);
    string errMsg = ex.Message;
    System.Windows.Forms.MessageBox.Show
(errMsg, "Error Message");
}

Thanks for your time and help.