You can upgrade to the Anniversary Update right now by clicking here to download the Windows 10 Update Assistant direct from Microsoft. The compact tool will be installed on your PC, and after verifying that there are no updates available for the tool itself, it will then look for the newest version of Windows 10 to install.
When you click the 'Update Now' button, the Assistant will scan your PC to check for any potential problems with installing the update. Once that scan is complete, you should get three green ticks for CPU, memory and disk space checks.
You can then proceed to the next stage of downloading the update to your PC. That can take a while, so you can minimize the Assistant while that process continues. When the update has finished downloading, the Assistant will verify the download to ensure that all requisite files are present and uncorrupted.
Once that's done, the update will begin. The process of upgrading will proceed as far as it can before eventually needing to restart your PC. When it reaches that stage, a 30-minute countdown will begin, to allow you finish off any important tasks before upgrading. You can also choose to continue the update immediately, or delay restarting your PC until later.
Once it restarts, the update process will continue, and as with other Windows updates, your PC will likely restart a few more times before it's finished.
When it's done, you should find all your files where you left them, with all the new features and improvements of the Anniversary Update ready for you to enjoy.