traditionally you use a heavy lawn roller but you need to find some one to do it for you.

how uneven is it? Is it just lumpy or sloping and needs digging out levelling and re-grassing.

If there are just a few hollows I find you can lift the turfs and insert fresh soil underneath.

its lumpy and the grass isnt great.I mowed yesterday and it looks better,my neighbor tells me the last owner never mowed he did it before i moved in which was nice,ty for answering

If the lumps are big clumps of coarse grass it might need reseeding with more suitable grass but if you've now mowed it successfully it sounds as though you'll be lucky...