I used the Arduino Uno Template in my pcb layout, but I don’t know how to connect the SCA and SCL pins. I am new to pcb design
Not sure how you got to this point without understanding that. But, top of the page,
You’ll see a tutorial.
No clue where the other pins are. You might have to switch to the buttom layer. Or watch some YouTube videos how to route in KiCad.
Or even solder in wire bridge …
Thank you. I used the not connect symbols to terminate them.
What is “them”?
You asked to route the SCA and SCL pins. I have no clue where they are, they can’t be seen on your first picture. I routed the only visible ratsnest-line. But if you marked SCA/SCL as no connect, then it is no wonder you can’t route them.
You need to provide more information, or this will end in an endless guessing game.
Also check with the Arduino people (forum?) for best practices for shield design WRT the I2C connections. It’s been a while since I’ve looked into it, but my hazy recollection seems to indicate SDA (not SCA) and SCL on the analog pins are for backwards compatibility to very early designs. For compatibility with future Arduino boards with different processors that continue to use the UNO form-factor, the SDA and SCL pins that are on pins 1 and 2 of the 10pin header should be used. As I said, my memory is hazy, so doublecheck before you commit your implementation.
You don’t need to connect SCL/SDA as they are duplicated on the Uno, they appear twice. Once on Analogue pins A4/A5 and again on the Digital side on pins 18/19, they are physically linked. You would do yourself a favour if you have an UNO pinout in front of you, just search Uno pinout and you can’t go wrong. And then you should go to your silkscreen layer and label all the pins as they are on the Uno, that way when your shield is in place you can see what the pins do. 
