As written by woodsmoke, you simply go to 'File -> Deployment...' inside RPG Maker MV. You can then choose the platform, among some additional settings.

That being said, the deployment process only prepares your project for further use, as you have to do further steps to get it ready.

If you want to upload it for play on computer, you usually only have to pack your deployed folder into an archive. The default way for this is to right-click your deployed folder and choose 'Sent to -> Compressed (zipped) folder'. The created archive can then be uploaded on platforms as a download or, as for itch.io, also as an direct html playable game. The latter may be a bit more work to set up though and might not suit every project. You can check out a guide about it here: https://itch.io/docs/creators/html5

The above is also a description for Windows. If you are on Mac, or want to create a deployment to be played on it, I would assume that it should be more or less the same process, but I cannot give any experience to add here.

For mobile, there are ways to make MV games run, but they are not as simple usually. That being said, I have not looked into that myself too much, either. If you just want to have it on your phone, I believe there might be software and/or apps that can launch them to variying results, depending on the project. If you want to officially get it onto the play store, I assume the process to properly package your deployed project to be allowed and run properly is more work and definitely needs a deeper reading via search and guides.

Hope that helps you.

I know how to get RPG Maker to the google  store, you have to make the HTML they give you to convert it for current day requirements. After which you must forever keep updating it because just like Apple google will force you to update or the app gets removed.