Null, Hi - how's it going?
John is very correct in saying to protect the laterals and do the complete backwash!

Hayward and I disagree on quite a few things in operating or maintaining one of their products - what to fill a sand filter with is just one of them. I say to add pea gravel first (replace ~ 1/4 of the sand lbs with the gravel) [see this for more info]
Having water in the filter before adding the gravel/ sand lessens the impact on the laterals. As John said, cover the pipe inside before adding the filter media. I've found that cutting one of the top corners off is the easiest way to get the sand into the filter, you make a ~ 'pastry bag'. If the filter is made of fiberglass (though I think the Hayward ones are 'plastic') wear a long sleeved shirt to prevent fiberglass splinters when you reach in to smooth the sand. Be sure to rinse the sand out of the threads and sealing surface when putting the top back on! Fill the tank with water before starting it up and as John says, give it a good backwashing immediately and a rinse.

I wish you well with the project and if I can help in any way just ask