First baby. If it is your first baby, then you will more than likely be expected to spend this early 1st phase at home. You may wish to contact your caregiver or hospital delivery suite or birth centre staff, to let them know that "It has started and is happening."
If your partner is at work, it may be good to have them at home now to support you, as the contractions become stronger. You may also wish to contact any extra support people, so they can plan their day (or night). You may not necessarily need them at this point, so if it is 2am in the morning, let them sleep, and contact them when you really need them to come. (They would only lie awake waiting for the next call anyway!).
Second, or subsequent baby. If it is your second or subsequent baby, you will probably need to contact your caregiver and move to your birthplace soon. Unlike first labours, it is more likely that you will progress more quickly and move straight from this phase into transition, (skipping, or having a very short active 1st phase of labour). It is possible for you to dilate up to 6- 8cms during this early phase, before the contractions become very painful (rather than only 3 - 4 cms like first time around). It is probably a good idea to get to your birthplace soon, before the contractions become too painful (and you need to stop and breathe through them to cope).