I Insert text at the beginning of the current line. J Join the following line with the current line. O Open a new line for input above the current line. If the text was yanked as whole lines, then the text is put into the text as whole lines below the current line. If the text was yanked as partial lines, then the text is placed after the cursor on the same line.
P Put the text before or above the cursor.
Replace the single character at the cursor with the next character typed. An ESC is not needed to exit the replace mode. Replacing a space with a CR is a good way to split existing lines. R Overtype existing characters, beginning at the cursor, until an ESC is typed. S Changes whole lines.