Before you can place a bid you'll need to request a DUNS number and register on SAM.gov. Then you'll need to link those accounts to your 18F Micro-purchase account.
Start by looking up your DUNS number on the Dun & Bradstreet website. If you've worked with the government in the past, you may already have one.
If you don't yet have a DUNS number, you can start by creating a Dun & Bradstreet business profile. You will need to use a browser other than Google Chrome, as the Dun & Bradstreet website does not currently support it. Once you've created a business profile, your DUNS number (and marketing materials, see below) will be sent to the contact information you specify within 30 days after your profile is created.
Please be aware that "as a result of obtaining a DUNS number, you [will] be included on D&B's marketing list that is sold to other companies. If you do not want your name/entity included on this marketing list, you must contact D&B … to request removal." (source) Our team is really sorry about this. It's an issue we're aware of and looking into.
Once you have your DUNS number, visit SAM.gov and create an individual account. The process is demonstrated in the video, below. Note that while registration physically takes about an hour, it can actually take about a day or two for the your application to be processed and for your information to propagate across various systems.
Be sure to link your DUNS number with your SAM.gov profile. Also, please note that auctions with a starting bid of $3,500 or more are only available to small businesses. If you're a small business, please ensure your Sam.gov profile correctly reflects this.
Once you have a Sam.gov account, you can either create a new 18F Micro-purchase account (using GitHub) or you can link your SAM.gov account with your existing 18F Micro-purchase account.
18F Micro-purchase uses your DUNS number to verify your registration on SAM.gov. To initiate this verification, visit your profile and update your DUNS number. The verification process should take no longer than a hour or so. Once you're verified, you're ready to bid.
To place a bid, simply find an open auction by visiting the 18F Micro-purchase homepage. Once you've identified an auction on which you'd like to bid, visit the auction description page and look for the auction's status box. If you're eligible to bid, you'll see a form that looks like this:
Enter a number less than the maximum bid (or current bid, if the auction's bids are not sealed) and click "Place bid". Good luck!