I looked inside the safe and there was only a scroll and the antique tool not the antique key.

The tool is the key. If you're not able to pick it up into inventory yet, make sure that you have fully read the scroll in the safe, and the diary in Boswell's desk.

I have the tool, but when I try to use it on Boswell tomb, nothing happens.

Did you fully read both the scroll and the diary from cover to cover?

OK thanks done all that and now I am in the cellar and have no clue which symbols to hit and what order. Does anyone have a picture of what these symbels look like so I can hit them in proper order

Here's a poster from the study which shows the symbols:



You need to find and press the symbols for Air, Fire, Earth and Water, in that order.