Sims interact with each other to boost relationships. Hover over another sim and
to interact. Choose a desired interaction to socialise with that sim. Watch the sims do whatever you selected then look above the head to observe the result. A + sign means good and a - sign means bad. Every sim has a relationship with every other sim.
You can see how that's going by
the relationship icon. What shows is what sims your sim knows and your sims attitude towards them. The first bar is daily relationship and is a short-term relationship. The bottom bar is lifetime and is long-term. Various icons indicate special relationships between sims. Note that relationships are not always recipricated. One sim can be in love with another but that sim could be repulsed.
You'll end this tutorial with a look at the wants/fears panel.
on the aspiration icon to view them. For more information see Tutorial 4.