Im trying to figure how to test AROS64, but don't know where to start.
Not sure if this is still relevant for you after so many nights have passed ...
Im trying to figure how to test AROS64, but don't know where to start.
I would probably say to start at the beginning

Depends on what you meant by testing
Do I always recompile from git daily ?
That would be a bit overkill in my opinion (although if it floats your boat then feel free to do so).
You can check the git commit log (
https://github.com/aros-development-team/AROS/commits/master) to see if commits were made since last time you checked. If there are not any changes since then, then it would be the same that you are testing (so that raises the question as of why to bother).
what is the process of it all. Thanks - new to Aros dev.
It depends on what you wish to test. If your aim is to test the new commits then you could do with downloading a nightly build and that would save you the trouble of updating/building the AROS tree.
Of course if the build process is something that interrests you or you wish to make changes to it then you would have to setup a complete development environment,
I have currently Installed on win10 64, VMware Player & following from this good guide :
http://vmwaros.blogspot.com/2019/09/setting-up-64bit-linux-development-env.html
AROS -> https://github.com/aros-development-team/AROS.git
Running on Win10 - VM Player -> Ubuntu64 18.0.4.3 LTS
Running on Ubuntu64 VM Player -> Linux compiled AROS
That is a good starting point.
Do we have any info on what has been tested & how & what to test etc.
Afaik there isn't a comprehensive list of things that are listed to be working (or not working) for 64 bit version of AROS so that would be trail and error.
How to test ? Well, you can try out some software then spot/locate the errors and report them (or try and fix).
I have beginner level understanding of C.
If you also have a beginner level of understanding of the AROS/Amiga api then you could make some simple test programs (there are also some of thiose programs listed in the AROS tree) compile them and test them.
Once you test specifc API or specifc parts of the AROS system then it usually becomes clear what things are not working as expected and in case you know how to read c ou could try and locate the offending code and attempt to locate what exactly is wrong that causes the error or ill-functioning.
Next step would be to try and actually fix the error.
Any info would be great 
I have not provided much information to go on but at least it is some sort of a start. I'm not sure if it helps you though, so please feel free to comment/ask :-)