Hello

I'm covering a fruit cake with royal icing and marzipan. 

My friend wants tappits lettering added. How do I fix the lettering. In fondant I'd use water, I can't use royal icing to attach as lettering is small. 

Any ideas? Ty

Sure you can use icing - just a tiny drop will do it.  OR you can make a strip of marzipan and attach the letters to it, then place that on the cake.  To attach the letters to the strip just lightly ice the whole strip.   The strip can have fancy edges or plain as you wish.