Hi @Dereshp and welcome to the forums!
I’m not sure if you were following a guide or anything like that but you have perhaps missed a step. Executing git push without any other options will try to push back to the Screenly app where you downloaded it from. Of course, this will give permission denied errors as the application is not open for the public to push code.
I’d recommend firstly taking a look at our recently refreshed deployment documentation to understand how the process works. If you’re completely new and have not set up your SSH key yet, I’d recommend using the balena push flow which requires installation of the balena CLI tools. If you’re happy using the git workflow though by all means continue with that, you just need to take a look at the section on how to add the remote which will allow you to git push to your device rather than back to the Screenly project.
Secondly, I’m aware that the official Screenly repo as it stands is not currently working with balenaCloud. The developers are in the process of updating it but until then I have made an unofficial fork which, at the time of writing, does work: https://github.com/chrisys/screenly-ose
I hope this helps, and don’t hesitate to post more questions if you get stuck again!