The following instructions are for namecheap.com but should be roughly the same for other registrars.

Sign in to your Namecheap account (Sign In option is available at the top of the page).
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​Select Domain List from the left side menu and click on Manage button next to your domain:
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Navigate to the Advanced DNS tab at the top of the page:
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In the Host records section (first section), click "Add New Record" button:
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In the Type column, select A Record, enter @ as the Host, COPY & PASTE 52.87.130.147 into Value, and click the check mark to save:
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Delete any other host records by clicking the trash can icon - do not perform this step if you are using your domain to point to anything else, or are using a custom email address (myemail@mydomain.com):
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To ensure your site works for people who are still in the habit of typing www before the domain name, you'll need to set up a "CNAME". It may already be in place, in which case you do not need to do anything. It should look like this:
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If it's not there, you'll need to add it:

Once you have done that, please see this article.