It is actually quite easy to apply Indian visa from Nepal, and even if you have foreign passports you can also be granted Indian visa in Nepal and not only from your home country.
So, first of all, you need to fill the visa form online. It is hideously long but manageable. Fill it before you go to the Embassy.
https://indianvisaonline.gov.in/visa/indianVisaReg.jsp
Here is what you need
1. Printed visa form
2. Photo (2″by 2″)
3. 4900 Nepali Rupees
4. Photocopy of your passport, Nepali visa, entry stamp to Nepal and previous Indian visa if any.
Then go to the visa section of Embassy of India. The address is 336 Kapurdhara Marg. It is opposite to British Council. And it is about 20 minutes walk from Thamel.
Then when you go inside, take a token number. Their office hours is between 9:30am – 12:30pm. There aren’t as many tourists in Nepal now, so you don’t need to worry about getting there early.
And if you don’t have your photos or photocopies with you, there are shops nearby which can provide you services you need.
The procedure will take you a week.
Your first visit will be in the morning. You will need to pay in the first visit.
And your second visit will be on the 5th working day (our first visit was on Wednesday and our second visit was on Tuesday) and also in the morning. Remember to bring your receipt and passport!
And your last visit will be the next day in the afternoon. And you will collect your passport.
It is very easy!:)