https://help.salesforce.com/apex/HTViewSolution?urlname=HTTPS-Security-Certificate-Switch-from-SHA-1-to-SHA-256-hash-algorithms&language=en_US

My Question is: How to do below 1st,2nd and 3rd steps ?

Please give me full description or any sample code.

any help is appreciated on this..
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To test the compatibility of an API client that uses SOAP to communicate with Salesforce:
1.  Set up an API client in a test environment.
 
2.  In that test environment, change the API client's login endpoint hostname from login.salesforce.com or [MyDomain].my.salesforce.com to sha2test.salesforce.com.
a.  As an example, change https://login.salesforce.com/services/Soap/u/32.0 to https://sha2test.salesforce.com/services/Soap/u/32.0 while leaving the path as-is.
 
3.  Log in with that API client.
 
4.  If you see an error message that resembles the following: "INVALID_LOGIN: Invalid username, password, security token; or user locked out." or “Content is not allowed in prolog.”, then this test passed and your integration can validate certificates with SHA-256 hash algorithms.
a.  The presence of this response means that the underlying TLS connection was successful, despite the higher-level error. The TLS connection is the focus of this test.
 
5.  If you instead see an error message that involves TLS or HTTPS, then the test has failed. Your API client will require adjustments or upgrades to operate properly with Salesforce, when Salesforce switches to the new certificates.

Thanks