You need to be signed in to the recipe cloud to download the recipe. The easiest way to do this is to use BeerSmith to browse the cloud recipes. In BeerSmith 3, you can click on 'cloud search' on the second toolbar down or you can access it from the drop down menu by clicking on 'recipes' > 'cloud search'. This will open up a window for you to type in the name of the recipe or search by name/style/type.
When you find the recipe you want, you can double click on the recipe to open it for viewing. If you want to download the recipe, then you can click on 'save a copy' to have a copy of the recipe downloaded onto your computer.
If you are on the web site, you will need to sign in using your user name and password to download the recipes. When you sign in, you will see a button to download a copy of the file to your computer which you can then open up in your copy of BeerSmith by clicking on 'file' > 'open file' and then navigate to the directory where the file was stored when you downloaded it.
Note that the recipe cloud on BeerSmith and the forum are two separate features and signing up for one does not mean you have access to the other.
You can find more information on Brad's blogs like this one: http://beersmith.com/blog/2019/01/06/beersmith-cloud-recipe-privacy-and-sharing-explained/