Perform this only after following the basic-pxe-server.md instructions.
Log on to your PXE server and then download the latest ipCore zip file and unzip it;
wget http://tinycorelinux.net/9.x/armv6/releases/RPi/piCore-9.0.3.zip
unzip ./piCore-9.0.3.zip
Now mount the piCore-9.0.3.img file we just download and check its contents.
mkdir ./picore_1
sudo mount -o loop,offset=$((512*8192)) piCore-9.0.3.img ./picore_1
ls -la ./picore_1
You should see a bunch of files which can now be copied to the tftpboot directory. But first we'll back up the existing tftpboot and make a new one;
sudo mv /tftpboot /_tftpboot
sudo mkdir /tftpboot
Now copy the new files over;
sudo rsync -xa --progress ./picore_1/ /tftpboot
ls -la /tftpboot/
You should see the same list of files as before but in the tftpboot directory.
If all the above was successful power up a PXE enabled Pi on the same physical network and it should now boot into piCore.