You can either use replacer mod to place them automatically or place them manually yourself. or you can use network skins 2 to replace them per-segment.

Where do I find these to place them?

this is catenary style for Railway Replacer Mod. Mod allows the replacement of map-wide catenaries. The other mod, Network Skins 2 also allows the replacement of catenaries, this time on segment, thus it's possible to mix different catenaries in a same map. Read the guide of the railway linked in the description / collection link.

do i really have to plop the catenaries manually? ive seen many videos while setting up rail it comes with a catenary. mine has just wire with no catenary at all

They are in the collection, just misplaced

Was this asset supposed to be included on the main Railway steam collection page?