Firstly, strings need quotes around them ( "cat","dog"... )
Have a string called guess. Make it as long as words[pickword], and fill it with ' ' or '-' or etc. Now what you need to do is ask the user for a char and see if that char is in words[pickword]. If it is there, Write it at the same position in guess. Example: if words[pickword] was "dog" and user entered 'o', guess is now "-o-".
If the char is not found, have an integer lives and subtract one from it.
Repeat this is a loop. If words[pickword] == guess, you win, if lives == 0, you loose.