if been as to take a photo for a a advert and told it needs to be 300dpi i shhot in raw and have not been asked for a photo to be a certain dpi size before any tips?

I dont understand what you typed

if been as to take a photo for a a advert and told it needs to be 300dpi i shhot in raw and have not been asked for a photo to be a certain dpi size before any tips?

I'm thinking,

"I have been asked to take a photo for an advertisement, and was told it needs to be 300dpi. I shot in raw, and I haven't been asked before to have a photo at a certain dpi before. Any tips?"

You can change your dpi setting in the raw mode if I am not mistaken, maybe someone can give you more detail than I can

There was something about it in the 'help' forum' not too long ago but I can't seem to find it.
It was being done after editing the raw and the dpi was changed in increments of 10% if I recall correctly. In photoshop it was done with the image resizer.
Hope someone with more detailed info can answer.

In photoshop you can change the dpi of a photo under "Image", then select "Image Size". You have an option in there for the dpi in the "Documument Size" box. Maybe this will help you get started, or raise a bunch more questions.