There are two ways to get Windows 10 Anniversary Update Build:
Via Windows Update:
1] Go to Settings > Updates & Security > Windows Update
2] In Windows Update simply click Check for Updates.
3] The Anniversary Update will appear as, Feature update to Windows 10, version 1607. Click update and the update will begin downloading and installing.
You can download the ISOs:
Click the button below to
[Note make sure you have at least 4 GB space on USB drive or, external HDD or DVD. Select Create installation media for another PC, then select the language, edition and version 32 or 64-bit. Save the file to a bootable USB drive or as an ISO. You can burn it to disk]