how to start??

You need to obtain a license first to practice as an RN in the US. Suggest that you read the Primer at the top of this forum for information that you need to have. You will need to pass the NCLEX-RN exam, and the series of English exams before you will be granted a Visa Screen Certificate and that is needed for immigration.

Currently, there are no visas available for work in the US with the green card, we have a retrogression in place. So coming on a tourist visa is not a viable option now, and is actually in violation of US Immigration Law to come to the US on a tourist visa with the sole purpose of staying and looking for work. Next problem that presents itself is that you can come for 90 days and not even need a visa, so you have to have a very good reason for them to grant the tourist visa for you. And you must have that one in order to adjust your status if they were available. You also would be in the US for several months without being able to work, so not always a good thing to do. There must be an actual visa to adjust and normally from France, you use the visa waiver.

Do not even start to look for a job until you have passed at least the NCLEX-RN exam, as no facility can offer you a job without having that done.

Please read the stickies at the top of this forum and then let us know if you have more questions. I would start with that.