I'm also using evening primrose oil for menopause. I use the 1000mg capsules and follow the dose recommendation on the bottle.
Along with vitamin E supplements, evening primrose oil is helping with my menopause symptoms. My main issues are difficulty sleeping, breast tenderness and hot flashes. Not only is the evening primrose oil helping with these symptoms but my skin is looking better as well.
I should warn however that it takes a while to start seeing results. It took about six weeks for me to start experiencing benefits. I recommend waiting for at least six weeks before giving up on this supplement. Of course, if there are side effects, that's different.