MBED 6 - How import library

Hi,
I’m working with MBED 6, using VisualGDB v5.5 on Visual Studio 2017 and I’m facing with a big problem; I’m trying to import an external library, made of an .a library file and an .h header file, but after many tries, I did not realize how to make it. Is it possible? And, if yes, how can I do? Please, could anyone help me to solve this problem?
Regards