Basically what was said earlier is true

you add verb stem + 입니다 and it makes the sentence more polite

for example 가다 - to go (this is the infinite form of this verb)

to say i go, all you need to do is to drop 다 and it becomes 가

However, Koreans are very keen on being polite. Therefore to someone older than you and someone you need to respect a lot you need to use the high form of politeness (they can actually get very offended if you dont speak politely!!)

so to make 가다 more polite you drop 다 and add 입니다 and so it would become 갑니다

to answer your other question as to where you would put the verb, it is ALWAYS at the end of the sentence.

So if you want to say 'Im going to school' to someone older than you or a stranger you need to say 학교에 "갑니다" rather than 학교에 "가"

I want to know when do I use the verb "입니다"?

thank u >o<

The meaning would be something like 'to be'.

'입니다' = VERB 이다 (BE) + ᄇ니다

You use this way of the verb to show respect. You may know that you add ᄇ니다 to the verbs that finish in vowel and for the consonants 습니다. I hope you understand a bit better :)