Like if you where building a game like rust
Make a Blueprint with the Mesh of the Item you want to place. Create something like an Inventory to store these items.
For the part of placing the item. Make a linetrace from your camera position in the forward direction of the camera. Multiply the forward vector by the length of the trace. When the Line trace hits the ground, break the hit result and spawn the object from your inventory or where ever you are storing it, to this position.
Everything else depends on the way you want to make this system. You can also preshow this item on the group by line tracing as long as you have the item in your hand and spawning it once. Then just change the position. Then, if the player presses left mouse button, you can finally place the object by leaving the position at the last point.
If this is too much for you, i highly suggest you to check some more tutorials. There should be tutorials on how to do this already! (:
Thanks for the info