Rabid Squirell said you can place your first trigger where you want - in a corner of the map - because this trigger is finally attached to helo in the 3rd step. But you have to decide what you want to do with it: which conditions want you triggering the task?
For your objective, you have 2 options:
- let the helo crash in a "random" position (after a setHitPointDamage for instance) and follow this solution to attach the trigger to the helo,
- or decide for (a) definite crash site(s) and you can simplify all of this. Just place the trigger(s) on it(them).
Crashing a helo with Vrotor damage is more realistic but a little bit more difficult.
That means you can script with setHitPointDamage, SurfaceIsWater test to avoid a crash at sea, waituntil conditions, spread crew in vicinity of the crash, create/attach crash site trigger as Rabid Squirell said.
On the other hand, you can manage a "fake crash" out of sight of players, mount your scenery with a helo explosion (setdamage 1), spawn or setpos each crew member where you want. Place simple trigger.
An alternate solution is to define 3 or 4 crash sites, and randomize the site. It's a mix of these above.
Btw, what solution you choose, you can also simply add a marker area on the map:
For example, the center of marker is in a 50 m radius of the true position of helo. More if you want.
_approx_pos = [(getPosATL <heloName> select 0) + random 50, (getPosATL <heloName> select 1) + random 50,0 ];
marker_crash = createMarker ["Ghost_Crashed", _approx_pos];
marker_crash setMarkerShape "ELLIPSE";
marker_crash setMarkerSize [70, 70]; // 70 m of radius (more than randomized radius to be sure helo is inside)
marker_crash setMarkerColor "ColorBlue";
marker_crash setMarkerBrush "FDiagonal" ;
marker_crash setMarkerText "Approx. Ghost crash position";
and addwaypoint to getmarkerpos for your different units:
_wp = (group player) addWaypoint [getmarkerpos "Ghost_crashed", 0];
_wpt_opfor = (group _bad_units) addwaypoint [getmarkerpos "Ghost_crashed", 20]; // optional: 20 for radius of opfor destination