Your original code is almost right. Just take a look at your structure definition. You want comments
to hold a string, but you have defined it as a single character. That's why you're getting an error with gets.
Now, gets won't allocate the variable for you so you'll need to use malloc
for comments
too. Or you could define it statically like in your second example.
If the user inputs more data than comments
can hold, you'll get undefined (and probably unwanted) behavior, so use fgets(currentC->comments, size, stdin);
where size is the number of bytes you've allocated for comments
.