Windows: use the Character Map or type Alt codes with the numeric keypad
Mac: press and hold the letter key, then choose the accented version
iPhone/iPad: press and hold the letter, then slide to the accented character
Android: press and hold the letter, then select the accented character
Microsoft Word: use Insert > Symbol or keyboard shortcuts
Google Docs: use Insert > Special characters
Linux: use the Compose key or Unicode input
Copy and paste accented letters from a character table
Change your keyboard layout to a language that uses accents
Use online accent generators or special character tools