Start the software.
Select New and select the HMI and the PLC.
Go to Help, Controller Help to find how to access memory in the PLC.
View, switch on Project Explorer.
Double click on Main.
Go to View / Toolbars and make sure that Objects is ticked.
Click on an object and then click on the screen and an a properties box for that object appears. Try Analog Numeric.
In the Analog Signal box type the PLC address, so for a Siemens S71200 I might type DB1.DBW16. That is the quick and dirty way.
If I wanted to select from a list of PLC memory locations I would go to View Name List and enter all the PLC memory locations I needed, or some PLCs allow you to Export and then Import, so that the list is automatically filled.