Here we go in-depth to describe how mechanical disc brakes work and offer useful tips as well.
And here our Park tool friend guide you on how to replace the brake pads on your bike
Attention: This guide aims to provide you with a reference for the task detailed. There are many more instructional guides online, so if you're still unsure, we recommend finding a guide you prefer. It is also worth noting that most bike shops provide brake bleeding as a service.
Remember, always be safe and test your brakes in a calm environment before riding in busy streets or on rough terrain . . . especially after maintenance such as this.
Link: Maintenance - Brake pads