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First, you need to have a developer account in Salesforce.
Go to http://developer.salesforce.com. Login if you already have an account or Sign up to create new one.
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Creating a new connected app and get Consumer Key (Client ID) and Consumer Secret (Client Secret) by connected app
Sign Go to https://ap2.salesforce.com/ and sign in your existing Salesforce CRM account and , then click Setup in upper right panel.
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Give your details and you will get the developer account.