You give no indication of the size of the yard but there are a number of ways of marking hard surfaces.
You could use the services of a contractor. A number of contractors offer car-park and road-marking services, including PA Marking Company of Leighton Buzzard (www.pamarking.co.uk). Also, search on the internet under "car park marking".
If you want to paint the lines yourself, you need to be aware that ribbed concrete can be difficult to mark. Common paints for use in car parks are thermoplastic paints and rubberised paints; there are other types but you will need to check details relating to their durability and uses.
Many marking liquids can be applied through sprayer-type line-marking machines, such as those supplied by Fleet Line Markers (www.fleetlinemarkers.co.uk), Grassline UK (www.grassline.net) and Vitax (www.vitax.co.uk). Others are best applied by the transfer method from a wheel. There are also aerosols for use with small-wheeled trolleys.