How to compare MFI data in S# Designer

Hi, I want to test a simple strategy that says:
Sell if MFI is above 70
Buy if MFI is below 30
What I have done so far is shown in the screenshot
Here's what I don't understand:
In the comparison object, the values to compare are only "Value 1" , "operator", "Value 2".
I am expecting to see something like "MFI", ">", "70".
How exactly do I design a logic that says "If the MFI is greater than 70, sell"
With the comparison object in my screenshot, doing this seems impossible because I cannot select "MFI" for "Value 1".