kore, sore, are - Use stand-alone
kono, sono, ano - must have something following them
kore - This
kono～ - This ～
Examples:
kore ha pen da - Correct
kono pen ha akai - Correct
kono ha pen da -
Incorrect
kore pen ha akai -
Incorrect
So you aren't taking a class.
Are you learning from text books?
If not (Or even if you are) take a look at this website for a start on grammar.
You will learn enough here to start basic reading in Japanese:
Tae Kim's Japanese guide to Japanese grammar - You must be able to read kana to use this website though, so it's a good chance to get to work on throwing away the Romaji
