How would I got about fixing this?

[SlyMaelstrom]

key_press = getch();
strcat (spell_word, key_press);

This doesn't work because, getch() requires key_press to be a CHAR and strcat() requires key_press to be a CONST CHAR (String).

Any way around that?

[Quantum1024]

Something like this

key_press = getch();
for (int i=0;spell_word[i];i++);
spell_word[i]=key_press
spell_word[i+1]=0;

You could also keep track of the length of the string somewhere to be more efficant.