Yep, the command @OliverV posted is what I used.
For reference, I found it on the main NCP page (https://ownyourbits.com/nextcloudpi/), the first thing under the “Supported Systems” heading where it says “Debian Stretch (all architectures)”.
To be clear, since you said you’re new to Linux, the install script itself is the install.sh file which gets downloaded from github. The command curl is a command line utility used to download files, and the vertical bar “|” or “pipe” sends the script that gets downloaded into bash, which actually runs the script.
As a heads up, be aware that the install script by default will put the entire NCP install, including your data directory, at the root of the system. So, for example, if you’re running the RockPro64 from a 32GB SD Card, that’s where your data directory will end up. I’m not of the best way of changing that. I followed some of the instructions here to move just my data directory to a couple of 4TB HDDs I had connected: HowTo: Change / Move data directory after installation That procedure is not officially supported, and may cause some issues, but it worked for me.