I bought the GDT game before it went on steam,and i dont know how to get my game in my Games Library on steam,so i cant access the workshop and all the stuff.
Thanks for replying and helping 
You should get a Steam key in your email, check it.
Hey, If you do not have your Steam key yet then check out this FAQ:
For a guided walkthrough on how to redeem a steam product code please visit this link:
https://support.steampowered.com/kb_article.php?ref=5414-TFBN-1352
If you have any further questions then let me know 