See this help page for instructions how to add published or unpublished research to ResearchGate: https://help.researchgate.net/hc/en-us/articles/14293005132305-How-to-add-research
There does not appear to be an option to enter a URL referring readers to an item published on a professional society website. Do you have a recommendation as to which publication type to chooese?
Unfortunately, there is no type "Report". I use "Data" in such cases, although this is not quiet correct. Concerning links to external sites, I add these to the abstract field like, e.g., in https://www.researchgate.net/publication/344474227.
As a part of the publication arrangement, the New Zealand Institute for Agricultural and Horticultural Science expect that authors ensure that potential readers are directed to their website, so they can keep track of the impact their publication channel is having...