1. Go to "My Citations" page of your Google Scholar 

2. Click on "Edit" button

3. Put your ResearchGate web url in the "Home Page" column

It is not very likely there is a way to do that, see this discussion and links therein

https://www.researchgate.net/post/Does_anybody_know_how_we_can_add_the_missing_citations_to_our_profile_in_Google_Scholar

There is no such option since google scholar harvests scientific articles by its own method. Usually it gets only a small subset of articles being published at RG and others scientific collaboration platforms so the citations is also a small subset. But google scholar claims that this subset is more realiable.

There is no way to do it! We are all complaining

First of all, I wonder whether citations have anything to do with Google's indexing system. Another explanation (though I doubt whether it is applicable to RG) is that if you published in a journal of debatable ethical editorial policy, that is, if both the publisher and the journal are deemed "'predatory journals", then Google Scholar would refuse to index it.

I am get confused have to tackle this situation as no one knows proper and satisfactory answer

We can use the link (Contact Us) at the bottom of the RG page and tell them about this problem.

RG answer your question in the help center

https://explore.researchgate.net/display/support/Stats+and+Scores

Hi

it will be automatically linked

1. Go to "My Citations" page of your Google Scholar 

2. Click on "Edit" button

3. Put your ResearchGate web url in the "Home Page" column

To put your Google Scholar Citations matrix in your ResearchGate profile.

1. Click "Info" button on your ResearchGate profile.

2. Click "Edit" button of "Website" under your "Contact" section

It is impossible to link them if the scientific journal is not indexed in Google Scholar

Researchgate is doing like Facebook that is popular among oldies nowadays.

I also keep trying to add... I HOPE NOT POSSIBLE

There is not any way to link them because of basic different in their data bank.

Thanks everyone for your response... still I'm looking for concrete step to increase the citations