As a Buyer, you can see a project from a Vendor's view without having to register for a Vendor account. You can use the Preview on Portal feature as long as the project is in the Pending or Open stages.
From your Details page of the project, click on the Actions button in the top right-hand corner. From the drop-down menu, click on Preview on Portal:
This will bring you to the Opportunity page that is visible to the Vendor for this Project:
The Supporting Documentation section will include all the Public Files you have uploaded. These are available to download for Vendors.
The Requested Information section outlines all required documents for your Vendors' submissions. This is where Vendors can download BidTable and/or Questionnaire templates if applicable.
Lastly, the Messages section will show the Vendors all of the Public Notices posted by you and/or allow the Vendor to send you a question via the Opportunity Q&A tab if you have Questions enabled for the project.
The Messages section includes the Public Notices and Opportunity Q&A tab.
Since you are logged in as a Buyer you will not see the Prepare Your Submission. This normally appears for Vendors under the Submissions section.