how do I update the files in /boot folder?

I'm currently using kubuntu 18.04 and I have a question. this is the content of my /boot folder:

abi-4.15.0-20-generic
config-4.15.0-163-generic
efi *folder*
grub *folder*
initramfs-4.15.0-163-generic.img
initrd.img-4.15.0-163-generic
memtest86+.bin
memtest86+.elf
memtest86+_multiboot.bin
retpoline-4.15.0-20-generic
System.map-4.15.0-163-generic
vmlinuz-4.15.0-163-generic

I can update my initramfs using dracut -f command but how do I update the other files? especially abi-4.15.0-20-generic and retpoline-4.15.0-20-generic since they're at the old version. I want to update them all and to know how to work with them when I need to. also how do I create vmlinuz files and what do they do?

The answer for most users:

• You don't touch those files. You do not update them. Leave them alone. Apt will automatically update them for you...when updates are available.

• That directory should properly have a set of files for each installed kernel. There should be two or three sets of files (two or three installed kernels). There may be differences between the sets: If one file is missing or extra, but your system boots properly, then DON'T try to "fix" or "repair" it -- it's not broken.

• Some of those files are essential for your boot. Do not try to "improve" or "update" or "clean" them or otherwise "help". Doing so incorrectly may result in an unbootable system. Leave them alone.