First, you should place text from Word into InDesign, rather than copy/pasting it.
I'm not an expert, but what I have read from the experts on the forum is that to use InDesign for non-English text, you used to need a non-English version of InDesign. It's not necessary for most left-to-right reading languages, but if you want to use a right-to-left language, you need InDesign ME (Middle East version), which lets you work with Arabic, Hebrew, and other r-t-l languages. I'm still on an earlier version of North American English InDesign, so I don't know if they have rolled these features into regular InDesign, but here is a link that may offer you some info: Arabic and Hebrew features in InDesign
Migintosh is right on the money. You need RTL tools to work with RTL languages. Your choices are to move to Creative Cloud (where you get the Middle East edition with your subscription) or to use third-party tools to work with Farsi in CS5.
I would recommend to subscribe to CC as it includes RTL languages without additional cost. With CS5 you have to buy either World Plugins or a ME version, both are investments which are not worthy for that old version.