1. Bloodline Forge Usage: Stash in the top right -> Bloodline Forge item Use button -> Select the hero you want to create a legacy from. That will use it (I should probably add a confirm button there). Then you'll have a new Item in your inventory, if you filter on Legacy you can see it. Each sub class has their own unique passives that they grant to legacies created from them
2. Archetypes simply copy over the Stat point allocation selection that you have and the weight config. The Skill Tree Builds are separate in the top left of the Skill Tree interface. You can either copy the skill tree of another Hero or save a Hero's current nodes as a Build and then use that to select Skill Points.