Assuming you are not using the module system, this is what you need to do:
If you have not already done so, I suggest you duplicate the folder "Native" (default path C:\Program Files (x86)\Mount&Blade Warband\Modules\Native), and rename it to whatever you would like your new mod to be called. In that way you will always have the default files to recover from mistakes, and still play Vanilla if you really hate this stuff.
1. Copy the contents of the Resource and Textures folders from this OSP to the corresponding folders in your mod directory.
2. Open module.ini in your mod folder, use ctrl+f to find the line "load_resource = materials_face_gen". Below that line, add these two lines:
load_mod_resource = men_at_arms
load_mod_resource = men_at_arms_lods
Save and close the file.
3. Open item_kinds1.txt in your mod folder. On the second line, directly under "itemsfile version 3", increase the number by 45. If you have no other mods installed, this number will be 603, and should therefore be increased to 648.
4. With this file still open, open the file included in this OSP named item_kinds_entries.txt. Press ctrl+a to select the entire contents of the file, then press ctrl+c to copy them. Go back to item_kinds1.txt, scroll to the very bottom of the file, place your cursor just above the line that begins with "itm_items_end...", and press ctrl_v to paste the lines for the new items.
Save and close the file.
5. Play game.