If you look at the multi-class notes its says that the Soldier gets two weapon proficiency of choice which are any two from the Soldier list and you gain proficiency in Light Armor.
The soldiers list is Pistol, Rifles, Simple weapons, Martial weapons, and either Advanced Melee Weapons or Heavy Weapons (player’s choice). Flame Throwers are an Exotic Weapon Proficiency, but you could take Advanced Melee Weapons (vibro bayonet).
Martial and Simple weapons are the basic weapons found in the PHB 5th ed. Scouts already get Martial Weapons so you don't need to take that one to get your proficiency bonus with longswords etc.)
Also Scouts get +1 to Fortitude defense so you take the best Defense if you are multiclassing they do not stack. So your Fort Defense will go up +1 (or 10 +2 Solider +2 heroic bonus +2 Con Bonus)
The soldiers list is Pistol, Rifles, Simple weapons, Martial weapons, and either Advanced Melee Weapons or Heavy Weapons (player’s choice). Flame Throwers are an Exotic Weapon Proficiency, but you could take Advanced Melee Weapons (vibro bayonet).
Martial and Simple weapons are the basic weapons found in the PHB 5th ed. Scouts already get Martial Weapons so you don't need to take that one to get your proficiency bonus with longswords etc.)
Also Scouts get +1 to Fortitude defense so you take the best Defense if you are multiclassing they do not stack. So your Fort Defense will go up +1 (or 10 +2 Solider +2 heroic bonus +2 Con Bonus)