You'll need SideQuest to install HereSphere on your Quest 2. You can get it from here:
https://sidequestvr.com/setup-howto
If you're only interested in testing out the demo, install the SideQuest easy installer. Follow the SideQuest instructions, and then search for HereSphere in the SideQuest web browser. Click on the "download app (itch.io)" link, which should take you to the itch.io page for HereSphere. And then scroll down to the demo link and click on it to install the HereSphere demo. In your Quest 2 app library, click on the drop down box in the upper right corner, then find unknown sources. HereSphere will be listed there.
If you want to install the paid version of HereSphere, you'll need to install the SideQuest advanced installer. Follow the SideQuest instructions, and then click on the down arrow icon in the SideQuest app on your PC, and then select the HereSphere apk file that you've downloaded from itch.io.
To stream SLR content with HereSphere, you'll need to click on the download links, which will use your SLR download quota. SLR no longer supports a public API for streaming their videos, so DeoVR will probably be better if you stream SLR content. If you want to stream videos from other websites like CzechVR, POVR/WankzVR, or NAVR, then they support the HereSphere web API, which allows you to view their library in a convenient web interface in HereSphere.