The only way is to mail RG team so that they add this specific journal. (and this way is not possible.. RG provides no support.. and if any, it`s really really bad support).
Try another platform.. I recommend you try Publons.. I`m not sure if they have this feature, but this one is much better.
Once, I found a similar post with this reply/answer:
If your journal isn't visible in the drop-down menu, it's not in our database. We're not currently adding journals to our database by request, but this may change in the future.