I recently bought a bird nesting box and put it on the top of a six foot fence.
What time of year should i see any activity about the box? Also should their be straw or hay inside?

They probably won't use it until next spring now, but its hard to say exactly when. You don't need to put anything in it, they will make their own nest. You can leave stuff out for them in your garden when they are building their nests for them to use. my friends emptied a bird box and found the nest was made from her old dog's hair.

Some birds nest (to rear young) until the end of August - with this weird weather you may get a second nesting season if we have a long spell of good weather. Birds will also use boxes as temporary roosts (like a motel!) so it may get use over the winter even if no actual nest is built.
If you really want to, large pet shops sell nesting material for you to hang in your garden, but don't put stuff inside yourself as this can put birds off - either from the human scent, or because they think another bird has already claimed it.

Thanks for your tips, i have not saw anythink going in and out yet see what winter brings.

Thanks Again.