When navigating through the portfolio discovery area, if you currently belong to a community/institution, you will be able to view content specific to that community. Just select your specific community from the Community Dropdown menu:

If you want to add your content to a specific community for viewing within your community discovery section, you have the following options:

1.) For personal portfolios, align your portfolio within the Style & Settings > Portfolio settings section:

2.) If you’re using a Course or Program portfolio, under Portfolio Settings, you can choose to allow your portfolio visibility by the entire community: