This is the forum for the 707 Captain for FSX, so I doubt we can answer that question here.

So.... I will take a guess at it... You might be able to open the doors using the Animations panel (IF the Legendary 707 has a 2D panel like the one in the 707 Captain).

The only other things I can suggest, are to read the manuals, or ask if anyone knows how it's done in the Legendary 707 - General forum.

Good luck. ;)