Check out example codes for "c# how to get a securestring from string". It will help you in understanding the concepts better.
Code Example 1
SecureString theSecureString = new NetworkCredential("", "myPass").SecurePassword;
Code Example 2
var s = new SecureString();
s.AppendChar('d');
s.AppendChar('u');
s.AppendChar('m');
s.AppendChar('b');
s.AppendChar('p');
s.AppendChar('a');
s.AppendChar('s');
s.AppendChar('s');
s.AppendChar('w');
s.AppendChar('d');
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