1031 Exchange

[Fred Ramos]

Hello to all. I am new to this site and have been investing in real estate for just over a year. I currently own 2 rental properties and am rehabbing my third. This 3rd property I believe has many options. purchased the property right. once the rehab is complete will have approx. 60% equity.
am thinking of selling to create a springboard into larger multi-families using a 1031 exchange (don't want to give uncle sam my money).
what I don't understand is the part of identifying the exchange property within 45 days. which property are they refering to?
also, like i said, I am new to investing so any help you guys/gals could provide would be greatly appreciated.
Thanks in advance to all :)