Your laptop has a 'combo-jack' which serves as both an earphones & mic input all-in-one. You have two options:
1) Buy a an adapter which converts your laptop's single combo-jack to two separate mic & earphone jacks.
OR
2) Buy a headset with a single jack-plug which incorporates it's own microphone. When you plug this in to your laptop's combo-jack, the laptop mic is disabled but you use the headset microphone instead.
Option 2 is my preferred choice because the active microphone will be right next to your mouth where it should be, so there's less external interference (eg other people or noises in the room) compared to using laptop's built-in mic.