To clarify abit, it seems you are using a custom activity from a third party library, possibly from the marketplace.
I expect you have a missing dependency error in the dependencies right?
As Peter explained, it can be done in a simple assign activity and you do not need this activity, so its likely easiest to convert them to an assign, where you specify the dictionary and key name on the left side and the value on the right as shown in Peters example.
Try implementing that and get back to us if you get stuck.