How do I record dtv on Seiki smart tv. SC-49AU600 using USB please?

I'm not familiar with the specific Seiki TV model sc55au600.
I fired up MyHarmony (Logitech) remote software because I use their Universal Remotes with all of my systems and while it recognized the brand Seiki it did not recognize the model SC-55AU600 as sold in Australia.

https://www.replacementremotes.com/ lists about 15 SEIKI remotes available with pictures so you can see if you recognize one matching your lost or broken one. Also, if you click on an individual unit it shows which TVs it is compatible with. I tried https://www.tvremotes.com.au but found no results for SC-55AU600. I would probably shop it on www.ebay.au which currently lists 85 remotes for SEIKI TVs.

The Seiki SE40FY19 is a Smart TV: Includes built-in internet connection that can be connected through WiFi or cable, includes TV apps, web browsing, and other online services. Yes definitely a Smart TV. These are the connections: 3 x HDMI Inputs, PC Input, Composite Video Input, 2 x Audio Outputs, Coaxial Digital Audio Input, USB Input.
Hope this fully answers your question.

hi if it not listed on booklet that came along with the controller
try using the automatic search best luck

Try this or select

Remote Control Code Lookup - DirecTV

https://www.directv.com/DTVAPP/content/remote_codes2

Usally these smart Tvs have their own app store it should be on the home screen where the preloaded apps are !

7x18

They have smart card slots, but don't use them for standard satellite usage.