This will come over time, but you can try to speed it up by choosing events in the calendar that reward more XP than other types of events - for example, Extreme Conditions, Historic and Training events (bonus points if the event has 5 stars in the description, meaning it's rare)
It is also worthwhile to obtain the "Gain XP" R&D perk in the crew tree as soon as you can, which should speed things up slightly.