GiFerro, you need to be careful it doesn't melt. Do you have a gas forge of a solid fuel forge?
If a gas forge make a little tray of stainless steel with the edges bent up so if the copper melts it's in the tray and can be easily removed.
If a solid fuel forge (coal, coke, charcoal,...) You may want to insert a 5cm stainless pipe with one end crimped over into the fuel stack to make an oven to place the copper in for heating. Watch it as the stainless will degrade over time and need replacing before a hole is burnt in it.
Expect to melt your piece several times before getting the right temperature *known* to your eye.
Working in a very dark area can help as the top temp for copper is a very low glow usually only see-able in a dark room.