There are no special materials or tools needed, other than your computer. I will demonstrate from my Windows 7 laptop. The process is the same on other operating systems, although some screens may have a slightly different appearance. I am not familiar with Apple products and how they do this.
Step 1: The Character Map
(First graphic) The easy way to find the Character Map on Windows 7 OS is to click on the Start button and begin typing "character map" in the box marked "Search programs and files." In the graphic you can see it also appears in the list of recently used programs because I did open it for preparing this Instructable.
(Second graphic) Click on "Character Map" in the list of returns, and Windows will take you to the Character Map.
(Third graphic) This is the Character Map. Use the pull down menu at the top of the dialog box to select the font you wish to use. Here it is Times New Roman. Scroll down the available characters to find the character you need. Click on it. The letter displays in enlarged size in a box. Some characters are similar. To double check that your selection is the desired character, look at the bottom line in the dialog box for the name of the character. This one is the Cyrillic Capital Letter De from the Russian alphabet. Click on Select and then on Copy. You may place more than one character in the window before clicking on the Copy button, if you need that. Go to your document and paste the computer's clipboard into the document. The Character Map contains alphabets and symbols for quite a number of languages.