My Wifi is really slow, please help!!

Hi guys,

I installed El Capitan on a spare hard drive, and I finally got the wifi working. However, it is incredibly slow, unlike my Windows partition, with 60+ Mbps. I would really appreciate some help! Here are my specs:

CPU: Intel Core i5 4690k
Motherboard: Gigabyte-Z97-HD3 Ultra Durable
16 GB of RAM
TP-LINK TL-WN881ND 300 Mbps
Western Digital 2.5 inch 750 GB hard drive.

Thanks in advance!