You should start with downloading Ren'Py from here:
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and play through the example projects which can be found in the launcher to begin with.
Once you are done, watch some tutorials that can be found on youtube about Ren'Py, such as:
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Once you can make something with placeholder graphics, you are done with the first part.
At that point you will need to replace the placeholders with actual graphics, and you can do that with DAZ3D which can be downloaded here:
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You can play around with it and, again, look for some tutorials on youtube such as:
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You will have few resources but they are enough to learn the software and rendering.
Once you have learnt the basics of DAZ3D, you should start importing new assets, and for that you will find this link:
https://f95zone.to/threads/free-stuff-for-daz-3d.22194/ quite useful.
It is a long progress riddled with many mistakes, but in a few months you should be able to make something.
Keep it simple, especially on your first project, good luck.