Knowing when to pay capital gains

Hello everyone.  Does anyone have an idea when I should pay the capital gains taxes on a home I just sold at the end of April this year (2018)?  I currently live in Pennsylvania and this house was a rental home for 10 years.
So, I'm not sure if I have to pay an estimated tax now OR if I can wait to file my taxes for 2018 and pay then without penalties.
Thanks in advance for any educated answers!