How do you call another sim over?

It's the button on the left side that looks like a wallet, go to the tab that has the two bodies and click the whistle

You can only call a sim over when they have no tasks. When they are free click on the "simtracker"at the bottom left of the screen. There will be two icons in each Sims area, one is of a briefcase (clicking on that gives you the option to send them to work), and the whistle icon, click on the whistle and they will arrive to the place you want them to visit. You can also go into the maps and say for example you want them to go to the Park, again wait until they are doing nothing at all, go to the maps, then click the location you want (I.e. The park) then go to the left hand box, click on the sim you want and then on the whistle and they will be there immediately (look at the entrance to the lot). Hope this helps.