Installation for most users should be straight-forward and easy. If you have a very old machine and the following guide does not work for you, please check out here how to install lubuntu on old and very old computers.
Before installing Lubuntu, be sure to disable Secure Boot and Fast Boot in BIOS, if the options exist. Some distros can work with Secure Boot enabled, but we still recommend disabling it for various reasons.
If you have Windows installed and wish to dual-boot, do the following: go to Power Options -> Choose what the power buttons do -> Change settings that are currently unavailable -> Disable “Fast startup (recommended)” and Hibernation, update Windows, restart, shrink Windows from within Windows using Disk Management to create “Unallocated Space” (preferably, at least 60 GB) for Linux, update Windows, restart.
After you’ve downloaded the ISO file. You will either need to burn this image to a DVD or you will need to put it on an 4+ GB flash drive. You can use the included software in your OS to burn it to a DVD.
Alternatively, you can put it on a flash drive. If you are creating the installer from Windows, you’ll need to download a tool called Rufus. To put it on a flash drive if you are creating the installer from Mac or Linux, you can use the built-in tool.
Visit this link
You can use inbuilt Startup Disk Creator to do it.
Reboot the computer and select the flash drive or DVD. If you disabled Secure Boot and Fast Boot in BIOS (if applicable), this should be easy.
When the image boots, select “Try”. You can proceed with the installation from “Try”, too, but the “Try” just loads up the live session all the way, which allows you to run programs other than the installer just in case we need to do other things. From the “Try” session, you should connect to WiFi if applicable, as WiFi is one of the most likely things to have problems working (it still works >95% of the time out of the box) so it’s good to check if it works from here.
If you have a single drive in your system and want the easy option, then you can select one of the easy installation options, such as “Install alongside [existing OS here]” or “Erase disk and install”. However, if you have multiple disks or want to have more control over configuring your partitions, click “Something Else” (fairly advanced).
(for single disks and simple configurations)
Ensure you can read your disk fine, if it have data on it. You can mount your disk by clicking the desktop icon.
Run the installer, select your language, and check both of the two boxes. Then, select either “Install alongside [existing OS here]” or “Erase disk and install”.
(fairly advanced, for multi-disk systems or custom partition setups)
gpt(typically capitalized: “GPT”).
fat32, with a name of “EFI System Partition”.
bootflag for your EFI system partition (the esp flag should auto-enable when you do this, if not, manually enable that too).
msdos(also known as MBR).
+to create a partition.
/dev/sd[letter]with NO NUMBER).
The rest of the installation should be mostly self-explanatory. You have to enter the username and password that you want, choose your computer’s name, set your timezone, etc.
Once the installation has finished, it will ask you to reboot. Do it, and log in.
If you are dual-booting, you should also make note of GRUB, the tool that allows you to select which OS you want when your computer starts up.
Source: /r/TechSupport.org, Click here