open A3_character_template.max and use its skeleton as a base to create your own character in a traditional way. An Arma 3 character has about 5 LODs and 1 shadow LOD. The typical polycount for LOD1 should be around 10,000 triangles and the final LOD should be small as possible (100 tris). Recommended shadow LOD polycount is 1000, all triangles, no smoothing, and closed geometry.
for info on organic modeling and skinning look for tutorials on the interwebz - there are plenty.
use only Skin modifier for weighting, use max 4 bones per vertex. You can speed-up the skinning process if you use “Skin Wrap” modifier, and transfer skinning from example character onto yours new one. Google “Skin Wrap 3dsmax” for details on how to use it.
if your character contains bare hands, legs or head, it is advised to use the standard Arma 3 ones for compatibility. Add them later in Oxygen, there's no need to do them in max.
to check if skin applies properly, you can apply some poses on the character. Either animate by hand, or Import “A2_animation_poses.fbx” and pick “update scene elements”. Arma3 animation poses in FBX will be coming soon.
all general rules of arma p3d models, textures and materials apply. If you need help getting oriented in O2, see Gnat's tutorial series
Run second O2, open Arma 3 character template P3D. Observe proxies in LODs (big triangles named “\A3\Characters_F\Proxies\headgear” etc) and some technical LODs, like Memory or Geometry, Fire Geometry etc. Don't touch any of this, add only your visual mesh. For safety, you can select them and press “Ctrl+H” to hide. Ctrl+A and Ctrl+Shift+H unhides all.
Ctrl+C Ctrl+V your character mesh into the appropriate visual LODs in the template file. (select in imported O2, ctrl+c, go to the template O2, go to the proper LOD, Ctrl+V)
if bare parts (hands, head) are present, then use existing ones already present in the template, just erase redundant faces covered by clothing.
copy-paste the shadow model into ShadowVolume 0.00 LOD. This one
must be closed geometry (Structure - Topology - Find Non-closed, Structure - Topology - Close)
has to be triangulated (select all, press “num/”)
cannot have any smoothing (select all, Surfaces - Sharp Edges)
shouldn't have any material or texture links (select, press “E”, erase paths)
cannot have any properties set in the Named Property window - delete them if there are any.
create injury selections - these function the same as in Arma 2, though they are called differently - the new names are “injury_head, injury_hands, injury_body, injury_legs”. These mark faces for which the material will be swapped for the injured version. Should be present on visual mesh only, make sure they are not on the Shadow model.
check selections “personality” (should contain actual head mesh), “hl” (contains hands and legs), camo, camo1, camo2 (contains clothing - depends on config, may vary from model to model - if not present then config has no influence on character texture)
if you don't want the game to display a head, helmet, glasses, vest or backpack on your character, then simply erase those appropriate proxies in all LODs. Note: a head proxy is called \A3\characters_f\Heads\bysta