[metapost] texmf/metapost/context/base, how can i use these macros defined in the files in this directory? thank you!

[mylatex mylatex]

Hi, everyone,

I found a toolbox in metapost and it's path is 
texmf/metapost/context/base,

How can i use these macros defined in the files in this directory? thank you!

I Just want to draw flow chart.
Could anyone can give me an example?

And should I study ConText?

Thanks

mylatex