There are many ways to enter a fada using your keyboard. But the quickest and easiest way I’ve found is to hold down the Alt Gr key and type the letter you need.
If you need a capital letter, just hold down Alt Gr + Shift key and type the letter you need.
Examples
Alt Gr + a = á
Alt Gr + Shift + a = Á
Some people use the combination Ctrl + Alt + letter, but I’ve found this problematic on my Windows PC, as it triggers shortcuts.
Let us know if these combinations work out for you, or if you've a different way you'd like to share.
Is fearr dhá theanga ná ceann amháin…