InfoPath Dev

I have written the formula in a notepad and pasted it in the button rule. How to use the field picker to select the required field could you please explain in detail sorry as I am new to this I am confused with these.

When I tried to add the below formula to the submit button rule I am getting error. concat("https://server/_vti_bin/ListData.svc/Equipment_federal?$filter=substringof('", EquipmentSearch, "', tolower(DESCR)) eq true") error is : "EquipmentSearch" does not point to a valid location path of a field or ...

Thanks for reply. I want to use filter in infopath form not in sharepoint. And I am new to inflopath forms could you please explain in detail of it. Thank you.

Hi I am using Infopath 2013. I need to use text filter instead of drop down because of huge list of data. How to implement wild card search for this text filter. I am using share point list as data source. Thnaks.