Arduino UNO/NANO <-> ESP8266 communication

Hello guys!

I have recently made a post in different section but someone told me that's it's only for "paid projects"? Anyway here I will try to explain better what's my problem.

I successfully programmed my UNO to read data from my DHT11 sensors, and to send it on my LCD screen, and same information on serial also. Works great!

Couple weeks ago I purchased ESP8266, first time I connect it to UNO, I managed to get replay OK when I type command AT. After I tested with blink example from Arduino IDE, after that I never managed to get replay. But it doesn't matter, I tried with setting a Webserver which worked on my wireless network, so I guess module is working like it should. OK

I have managed to post data from ESP8266 to my MySQL database without a problem.

Thing is... how can I make ESP8266 gets data from Arduino UNO board? Arduino UNO has several senors and I want that data instead of going to display or serial to go to ESP8266 which will post it to my Mysql (PHP and Mysql are no problem for me).

I stuck on how to send data from arduino UNO to ESP8266? I've seen alot of tutorials but I don't know what part of the code needs to go on ESP and what part of the code goes to Arduino? In that case, how does TX and RX needs to be connected, and where?

Thanks guys!