Hi @belotomindzo
My first recommendation is to lower the dpi scaling on your display, so you see the ribbon commands properly. For 1080p, I recommend 100% scaling.
That message is actually a tooltip that follows the cursor to show options you can use during placement. You can hide it from the contextual ribbon, during placement, by toggling the show tooltip command.
You can place shape driven rebar in 2D views and you can place free form rebar in 2D or 3D views.
More info about rebar placement here:
https://help.autodesk.com/view/RVT/2023/ENU/?guid=GUID-D61AF551-AD15-4FEC-966F-C048E0885212
Depending on the placement plane and placement orientation options, when hovering the cursor inside the host, you will see the rebar expand to fill the host (expand to host option) or can specify a box to which the shape expands (placement by two points).
You also need a valid host to place rebar inside. Here's more information about what elements in Revit can host rebar
https://help.autodesk.com/view/RVT/2023/ENU/?guid=GUID-70325142-8824-41F5-95ED-9E55C1188952
Ovidiu Paunescu, M.Sc. Str. Eng.
Sr. Product Owner | Autodesk Revit