Tails 5.1.1 (and many other versions)
For MBR legacy boot from the ISO (DVD) file, use an extension of _.isodef.iso and E2B v2.14 or later.
For UEFI, use agFM and in the Tails grub2 menu, if you have a USB HDD, choose the 'Tails (External Hard Disk) option.
Tails 4.2, 4.6 4.28, etc.
Also see here for UEFI boot and later Tails versions with E2B .mnu support.
Tails 3.16
The Tails ISO can be downloaded from here. You can download via the Torrent or download the ISO directly.E2B will boot from a Tails ISO on a real system from a Removable E2B Flash drive.
Booting from ISO under a Virtual Machine will not work if the VM sees the USB drive as a 'virtual IDE/SCSI hard disk. (E2B v2.14+ will boot Tails ISOs on both Removable and Fixed USB drives however).
If your E2B USB drive is a 'fixed-disk' type, then you can convert the Tails ISO to a .imgPTN file. Ensure that 'live-media=removable' is not in the kernel cheat code line (press TAB in the syslinux Tails boot menu to see the boot parameters). The latest versions of the MPI Tool Kit should remove this cheat code for you if you choose AUTO-CORRECT=Y.
The persistence option in the Desktop menu system cannot be used because Tails will only create the persistence volume on a USB drive that has been installed using Tails (has a GPT partitions with a volume name of 'Tails' - possibly only works on Removable USB media?) and so has the correct partition structure.
Tails 2
The Tails 2.2 ISO can be downloaded from here. You can download via the Torrent or use FireFox and download the ISO directly.The Tails 1.0 and later ISOs cannot run with persistence now (unlike earlier 0.xx versions). Tails 1.0+ looks for a GPT disk and an EFI volume labelled 'Tails' (see here and here), so you must make a dedicated GPT USB Flash drive for Tails if you want persistence. If the drive wasn't 'made by Tails installer' then it will refuse to create a persistent file system for you.
If you boot from the ISO (even in E2B), you cannot install Tails to a new flash drive because Tails will only install if it is running from a USB FAT32 drive. This is a real pain!