Since Croatian is language that is pronounced as it's written (at least in most cases) I would suggest learning pronunciation first. That will open you room for reading out of loud, to get acustomed to voices and croatian words. 

Here you have some resource for it: http://mylanguages.org/croatian_alphabet.php ;

After that probably best thing is to start with basic conversation with someone here, or listen to some music. I will try to find some easy vocabular songs latter. 

Very important for learning Croatian is not to be perfectionist and trying to learn all the grammar rules at once, beacuse there is a lot of them :) 

It's ok to miss noun case endings, gener and stuff like that :)

Hello, Sally !

The first best step is to have a good will and strong motivation for learning language. ;)  I suggest you start from basics (alphabet, salutations, some easy sentences - learn a syntax order or structure of sentence.) Also, you can watch Croatian movies, listen our music (depends on your musical taste). Did you try to find some text books ? It important to pratice every day. Write down all the words you hear or read, build your vocabulary and don't be afraid to ask questions. Croatian might be difficult to learn, but it's not immposible. Do your best. :D If you have any questions, or need help please ask.