❔ How to reference older versions of system.windows.forms?

Hello all. Daft question: how do I choose what version of system.windows.forms my project compiles with. Presently it does so with 4.0.0.0 which breaks 3rd party libraries I'm using due to their use of ContextMenu. I've tried lowering my Framework version, but it still seems to build with 4.0. Also, wanting to stick with Framework, not Core...