Very simple browse to your /boot directory
It does make more sense to extract the image in its own directory eg "initramfs-blabla-dir" as it will literally extract directly to the pwd.
cp initramfs.img someotherdir
cd someotherdir
zcat initramfs-3.10.0-514.el7.x86_64.img | cpio -idmv........
Copy the initrd to somewhere else, say /tmp:
mv initrd.img to initrd.gz
*the mv to .gz is needed otherwise gunzip won't work/it will refuse to operate without the correct .gz extension
gunzip initrd.gz
cat initrd | cpio -idmv
The last command extracts the contents of initrd to your present working directory.
For 7z .lz initrd........