I have been working with eportfolios for teaching and supporting students since 2013. I was the Chair of the Centre for Recording Achievement and have worked with JISC (the Joint Information Systems Committee) other universities to support the development of digital literacies for reflection and learning.

An ePortfolio is an electronic collection of artifacts which can be text, videos, photos, social media etc. By bringing these things together and providing context it opens you up to be more than the 2D self, using online tools like ePortfolios allows you to become 3D (online).
An portfolio can be anything on the web that brings together sets of online items. With text to reflect and even video to comment they are very good at providing an outsider (could be a mentor, employer etc) an insight into your skills and experience.

They should be clearly signposted, easy to find and obvious what the message is.

There are two main tools at UCL that you can access. My Portfolio (based on a real portfolio tool) and Reflect which is a blog that can be used as an portfolio.

There are useful resources to help guide you, almost step by step. These include text information as well as videos outlining what you need to do from start to finish.

For Reflect https://mediacentral.ucl.ac.uk/Play/23258

For MyPortfolio https://wiki.ucl.ac.uk/display/Mahara/MyPortfolio+Resource+Centre+-+home

Link here for the Pathbrite user guide https://pathbrite.com/userguide/1/en/topic/create-portfolio
Specific Student User guide here
https://pathbrite.com/student-userguide

Feel free to get in touch with me if you need some support in setting up your portfolio. Or if you have any questions.