First go to Pinterest.com and log in with your Business Account credentials. 

Step 1.View your profile. Click on the board you want to pin a photo to.

Step 2.To pin a photo or video click “Save A Pin” on the left.

You will see 2 options in the drop down menu:

Select the “Your device” option to upload a photo from your files or home computer.

or

Select “The web”  to paste a URL and choose one of the photos to pin from that URL.

Step 3. After the picture is done loading it will ask you what board you want to put it in. Select the Board you would like to Pin to and click “Pin it”. The Pin will then be on that board.