First, take a knife and scrape it gently along the seam of the pen. Every time you scrape, the seam of the pen will become a little bigger and the water output will increase. Try to see if the water output is appropriate on the paper, and don't scrape it if it is appropriate.
Secondly, after some pens are disassembled, the nib will have a slider, and the water output can be changed by moving the slider. When this pen leaves the factory, the slider is always at the place with the smallest water output by default. This method only applies to some pens, because not all pens have this slider. As far as I know, Ling Mei has pens. This method is not recommended because beginners can easily take apart the pen.