I have an ok understanding of apex and I am new to VPM (Flow Designer).

I am trying to get "Apex Callout" to work with a class i have but am not getting anywhere. After opening the flow designer pdf i came across the following statement:

"The visual Apex callout element allows you to call an Apex class with the Process.Plugin interface"

What is the process.plugin interface? because i am getting the following error when uploading the flow into Salesforce

"ErrorWe had trouble uploading the flow. Apex class does not exist or is not a plugin class: FlowDesignerISA.GetISAamount"

I have an ok understanding of apex and I am new to VPM (Flow Designer).

I am trying to get "Apex Callout" to work with a class i have but am not getting anywhere. After opening the flow designer pdf i came across the following statement:

"The visual Apex callout element allows you to call an Apex class with the Process.Plugin interface"

What is the process.plugin interface? because i am getting the following error when uploading the flow into Salesforce

"ErrorWe had trouble uploading the flow. Apex class does not exist or is not a plugin class: FlowDesignerISA.GetISAamount"