Germination occurs within a month. You must remember to water the soil while maintaining constant humidity; if the soil dries out, the plant dies, so before adding water it is a good idea to check. You may not even need it. If the first 6 mm are dry, it is advisable to give water, otherwise not. Excessive amounts of water can cause  bacterial proliferation that destroys the seedling. 

Once it has sprouted, remove the bag, leave the plant free and continue watering as normal. When the time comes, that is, when the olive tree has grown 18 cm, it can possibly be transplanted in autumn. Once the tree is buried, it is watered as usual and then its growth is monitored.

After a few years you will be able to harvest beautiful olives. There are trees that bear fruit after three years while others  need at least 7/12 years.