recently purchased this gun in almost new condition.The problem is it didn't come with the lower rail so that I can install a sling.What do I have to do to correct this? Also is this a older or newer version of this gun serial no. DEH5062. Thank for any help. John

If you have the Gen2 with the Mlok handguard then you are going to either have to put a Mlok picatinny rail and attach a sling point to that, or just get an Mlok sling attachment point. If you have a QD point on your lower then you can attach to that.
Either way to attach a sling to the handguard you are going to have to source an Mlok rail or direct sling attachment.

In this google will be your friend
mlok sling point - Google Search

ON my old one I drilled a hole in the bottom of the hand guard and screwed a quick detach stud(wood thread) into it.....Works fine......

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S&W Accumulator

Newer since there is no rail.
Get the key-mod sling swivel adapter. There are push button versions and the old QD style

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Buy cheap, pay twice.

Thanks a lot for your informative replies,very helpful.