Hi,
You will need to keep giving the kid milk (in England you can get dried goatsmilk powder but I don't know about Spain.) for at least a few months. During this time they will also start to eat grass and branches, and cereals such as maize. Goats are browsers rather than grazers so much prefer hedges and trees. You will need to protect the trunks of your trees as she will eat the bark. They like their food clean so it is best put in a hayrack or tied up above them. She will also need shelter from the rain ( they don't have much of a coat to protect them from the weather) and a run with decent height fencing. When they are older they can be tethered so it is best to start getting it used to a collar and lead. If its a male goat you've got then you will have to get it neutered asap otherwise you will end up with a large , very smelly animal. However goats are lovely, funny, clever animals and having one from two days old means it will think it is one of the family-not a goat!