Depends what you mean by “best”. Personally, I use Lubuntu, as it is an ideal combo of features vs. resource lightness for me. Linux light and Puppy Linux are also among more popular lightweight distros.

If you like debian you could try crunchbang++ and Antix.

Or you could install arch or void linux and configure it minimally with xfce or some window manager.

If you want something fresh , checkout nixos. I have had nixos on my desktop for less than a month now and I’m already considering sticking with it for the forseaable future.

Download BalenaEtcher and burn an .ISO of your selected distro to a USB memory stick - Pop!OS and Linux mint are perennial favorites. Bear in mind that this will erase all data from the stick.

Boot the laptop into BIOS (you will need to check with the manufacturer to see which key you will need to hold to do so) and scroll down to the “boot from device” or similar option. Select “Boot from USB”, save settings and reset your laptop.

If all goes well, and your laptop likes the distro, you should see a bunch of cryptic text scroll by. Don’t worry, this is what Linux shows instead of a loading screen. A menu should pop up, asking you if you want to try out the Live distro, or install the OS. Choose the live distro first, this will create a version of the OS that works from the RAM disk and does not install on the hard drive.

You can now play around with the OS, browse the internet, play games, anything except saving locally to the hard drive (unless you Mount it, but that’s another story). When you are good and ready, you can either choose to dual boot to Linux and Windows, or take the plunge and use Linux as your primary OS!

Hope this explanation wasn’t too rambly. Have fun!