Wielding Weapons
When the rules refer to wielding a weapon, it means you are holding a weapon with the correct number of hands and can thus make attacks with it. For example, if you are holding a small arm or one-handed melee weapon in a hand, you are considered to be wielding the weapon. If you are carrying a longarm or two-handed melee weapon in one hand or wearing a holstered or sheathed weapon, you are not wielding that weapon.
Source
Core Rulebook pg. 243