If someone is still looking or will be looking for answer, here is the way:
In plugin solution you need to add instance of concept IdeaInitializerDescriptor (from language jetbrains.mps.lang.plugin).
There will be dependency section, where you can add dependency on Idea or MPS plugin. For MPS plugin you can choose reference from auto completion menu. And for Idea plugin - create new instance of IdeaPluginDependency concept and specify pluginId (string), where pluginId will be identificator of the Idea plugin, you want to depend on.
If someone is still looking or will be looking for answer, here is the way:
In plugin solution you need to add instance of concept IdeaInitializerDescriptor (from language jetbrains.mps.lang.plugin).
There will be dependency section, where you can add dependency on Idea or MPS plugin. For MPS plugin you can choose reference from auto completion menu. And for Idea plugin - create new instance of IdeaPluginDependency concept and specify pluginId (string), where pluginId will be identificator of the Idea plugin, you want to depend on.