How do I delete files from my Startup Disk when it's full?

[iMore Question]

i have only had the mac for about 6 months and don't really use it for files etc so i can't see it being full, unless someone can lead me in the right direction to the files i may not know about

my mac keep saying startup disc full, delete some files. how do i do this as there isn't much on my macbook air

 

[Just_Me_D]

You've or someone else saved files, pics, videos, music, etcetera to the "startup" disk instead of a different disk/partition. Move those files from the "startup" disk.

https://support.apple.com/en-us/HT204417

The Mac ?Startup Disk Almost Full? Message and How to Fix It | OSXDaily