There are many reasons why you might need to bleed your brakes. Remember before doing this to verify your brake pad wear.
You will need Bicycle Rated Mineral oil like Shimano or Tektro which can be easily bought online and a Bleeding Kit
Here we add the two best descriptions of how to do it
This is a quick 5 minute written tutorial from our friends at epicbleedsolutions.com
And here is a detailed video from Amstudio
If you have any questions please contact our techs at firstname.lastname@example.org
Attention: This is a guide to provide you with a reference for the task detailed. There are many instruction guides online that can help and also local bicycle repair shops that can perform this task. Always be Safe and test the result in a calm environment before going on a test ride