Could you explain whey they use "on" in thoes sentences?
This writing below is from my book.
On third line, there are words like "on how others"
and on forth line, there are words like "on how to combat it".
I want to know why they use "on".
Could you please explain it to me?

First, the person need to accept that he has a problem. Then, he
should get some information from books, other people, or the Internet
on how others have fought the same or similiar types of problems.
Next, he should make a plan on how to combat it. The last step is
actively working to end an addiction.

Question

Could you explain whey they use "on" in thoes sentences?
This writing below is from my book. 
On third line, there are words like "on how others"
and on forth line, there are words like "on how to combat it".
I want to know why they use "on".
Could you please explain it to me?

First, the person need to accept that he has a problem. Then, he 
should get some information from books, other people, or the Internet
on how others have fought the same or similiar types of problems.
Next, he should make a plan on how to combat it. The last step is 
actively working to end an addiction.

Answer

"on" in this context just means "about" or "on the subject of."

Answer

Different verbs take different prepositions. They are verbal phrases and each verbal phrases and its meaning needs to learnt, unfortunately. 
In this sense, you could substitute 'on' with 'about' in order to get the meaning.

But it would  ot unnecessarily be grammatically accurate to do so. Just do that to help yourself understand the meaning.