The game itself takes roughly 50GB of space, and requires an online connection to use. This also means that you will need Xbox Live Gold or Playstation Plus to play it on a console, but you can test it for free on PC without any subscriptions.
The trial will run from now until June 17th, so make sure to go ahead and test it as soon as you have time for it. There are no gameplay limits to the game, so you can play the entire thing if you manage to do it, but you will need to buy the game if you want to keep playing after the 17th of June.
Download and play the Fallout 76 trial on Playstation 4To test Fallout 76 on Playstation 4, either go to the store on your console, or from a web browser on a computer or mobile. Once there, search for Fallout 76 and bring up the store page for it. Below the "Buy it now" option, there is another option called "Test Free Demo", so click on that. That will take you to the checkout menu, but with a sum of $0, so just keep going until the trial is added to your account.
The next step is to click on "Download now" to begin the download for your Playstation 4. As mentioned above, it's a 50GB download, so expect to spend a good while downloading it.
Download and play the Fallout 76 trial on Xbox One
Go to the Microsoft Store either on your Xbox One console or on a web browser from a computer or mobile, and search for Fallout 76. When you are on the product page, just click "download" and it will begin to download the free trial.
Download and play the Fallout 76 trial on PC
You can download the Fallout 76 trial for PC on the Bethesda Store, so again, search for Fallout 76 from the store. Make sure to log in first though, or else the trial option won't show up. Anyone, once you are logged in and have found the Fallout 76 product page, click on "Download" to begin downloading it, and then just launch it once it's finished.