Windows: use Alt codes or the Character Map
Mac: press and hold the letter, then choose the accented version
iPhone/iPad: press and hold the letter, then select the accent
Android: press and hold the letter, then select the accent
Microsoft Word: use Insert > Symbol or keyboard shortcuts
Google Docs: use Insert > Special characters
Copy and paste accented letters from a character map or online source
Use an international keyboard layout for faster typing
Use Unicode input methods if your system supports them