Do I have to start the participants using a launcher script or using some special arguments?
In order to start a coupled simulation, you can execute the (adapted) participants normally, as you would execute them for a non-coupled simulation. “Adapted” means either that the solver is modified to call the preCICE library, or that it loads a separate “preCICE adapter” at runtime. Often it is helpful to just start the simulations in different terminals.
Please note that that the solvers call preCICE (as it is a library) and not the opposite. There is no “preCICE executable” required to start the simulation.