I am trying to georeference my map, But I am unsure how can I rotate my image so that I can find GCP points easily from map canvas.
In this image North is clearly visible.
Using qgis 3.0.
There are several tutorials on how to georeference an image. Consider using a search engine with some keywords before asking on this Q&A site.
I typed in georeference + qgis in google and found this QGIS tutorial on Georeferencing Topo Sheets and Scanned Maps.
You can do a quick 90-degree rotate in paint or whatever, as suggested in the comments. Then you can georeference using J Rectifier plug-in. Here's a video on J Rectifier: https://www.youtube.com/watch?v=xLMvIUtdBJ8