There are four stations in the museum that can be used to craft replicas of items that can be displayed in the museum.
The main station is the Replica Station found in the Curator's Office. Most relics can be replicated at this station, but some, like books and wines, spirits and ales will need to be replicated at one of the other stations instead.
The second station is the Scribe's Desk which is also found in the Curator's Office. Here you can mainly make copies of quest books. To use the desk, you need to sit on the chair in front of it and the crafting menu will open.
As long as you have had the original relic in your inventory, you will be able to craft it, even after it is handed in, so there is no need to craft a replica before you complete the quest associated with the original relic.
It is possible to make more than one replica of most relics. The first time you have made a replica of an item, you will no longer be able to craft them at the stations above. If you want more than one replica of an item, you can go to the crafting stations in the safehouse where it will then be possible to make as many replicas as you want of the item. This can only be done after you have crafted the replica for the item once at one of the museum crafting stations.