step 1: Creating a bootable usb drive
Insert USB stick and open Rufus. Select your usb drive in the "Device" drop down menu. Beside "Create bootable disk using" select "ISO" and click the disk icon. Select your Ubuntu ISO and press "Start".
Step 2: Boot Settings
On the computer that you are installing Ubuntu on, enter the BIOS. This can be done by pressing F2, F10, DEL, etc. (depending on motherboard manufacturer). In the BIOS, change the boot order to boot from USB first (Or alternatively, you may use a boot override feature). Restart your computer with your USB drive connected and it should boot into the Ubuntu installer.
Step 3: Installation
Once you've arrived at the installer, click "Continue". Select both options "Download updates while installing Ubuntu" and "Install third-party software for graphics and wi-fi hardware, Flash, MP3, and other media" and click "Continue".
On the "Installation type" page, choose "Erase disk and install Ubuntu" (Note: if you want to play with other storage settings you can do so here). Click "Install now", then "Continue". Select your location and click "continue", "continue".
On the "Who are you?" page, enter all the fields and click "continue". Ubuntu will then proceed with the installation.