in androidstudio 4
add the sdk using the sdk manager
I use android SDK build tools 23
you have “matchndk” install 23 and put 23 there or alternatively install the sdk to “match” the ndk
I suggest sdk23 tho
I use ndk 21
sdk cmd line tools latest 6 or 7
I use sdk platform 6 marshmallow
this is a good tutorial
don’t get frustrated, it took me 3 weeks to get it right