To use the MPLABX IDE for debug and program the PicsimLab, install the plugin com-picsim-picsimlab.nbm in MPLABX.
The plugin connect to Picsimlab through a TCP socket using port 1234 (or other defined in configuration window), and you have to allow the access in the firewall.
Tutorial: how to use MPLABX to program and debug PICsimLab.
It's possible import and debug a Arduino sketch into MPLABX using the Arduino import plugin.