The Gaelic language family is divided into distinct branches, including Irish Gaelic and Scottish Gaelic. Irish Gaelic is more commonly just called "Irish". It is a Celtic language that is part of the Indo-European language family.
Irish is written in a variation of the Latin alphabet. However, it also uses characters with diacritic marks, including á, é, í, ó and ú, to indicate various aspects of pronunciation. There are two methods for typing these characters.
The simplest method is to use the character suggestions. To do so, type the base character for the letter you want, then select the special character from the set of characters which appears.
The other method is to use the virtual keyboard with the layout set to Irish. When this virtual keyboard is active, holding down the Ctrl and Alt keys at the same time will provide access to special characters. Capital letters are available by holding down the Shift key as well.
See Typing Accents and Special Characters for details on both typing methods.
To an English speaker, Irish words often look very different than they sound. As a result, Irish spelling can be tricky for English speakers to master, no matter what method they're using, but that doesn't mean it can't be done. Just take your time, and work with each lesson as many times as you need to learn it. Keep your learning sessions short if you ever find yourself getting frustrated - you don't have to finish a lesson in the same session you start it. Remember, too, that there are a number of non-typing activities you can focus on when you don't feel like typing the Irish words. The more different ways you experience the language, the better you'll learn it and the more fun the learning process will be.