"ESPN3" brand just means it's online streaming only, and there is no channel you can tune in to watch it.
There are multiple ways to access that online stream:
- use your computer, and go to watchESPN.com in an internet browser
- use your phone or tablet, and download the watchESPN app for that platform
- use your smart TV (device), such as a Roku, AppleTV, etc., and download the watchESPN app for that platform
- it might even be possible these days, if you have a new enough cable TV box, that it's smart enough to have a watchESPN app built in (I know some cable TV boxes now support Netflix directly)
Usually, you then need to authenticate with your username/password for your cable TV and/or ISP account. Like your Comcast Xfinity or Charter Spectrum login info, etc. But perhaps these particular events will be allowed to be accessed by anyone for free? That's the only part I'm not sure about