From the normal mode you can use these commands to jump into insert mode in different ways. Insert mode is where you enter text similar to a regular text editor. Use the escape key to go back to normal mode.
Insert before the cursor
Insert at the beginning of the line
Insert (append) after the cursor
Insert (append) at the end of the line
Insert (open) a new line below the current line
Insert (open) a new line above the current line