A few easy tips to remember and study will be stable parameters! Purchase a few different test kits to help keep things stable. Try not to go cheap on test kits or equipment!
The biocube is a nice beginner tank!
The back section of the tank on the left corner is where the return pump chamber should be, towards the top of the chamber on the glass there should be a marker for your water level......you will need to check that DAILY! The water level in the return pump chamber will drop fairly quickly in that biocube. Also i would remove the bioballs from the center chamber and fill it with liverock rubble...
The chamber to the right where water enters can be used as a refugium to house chaetomorpha algae( which helps remove nitrates and phosphates) and will also host copepods and other beneficial critters!
For now after your initial cycle and your ready for fish, the 2 most important things will be keeping your temp completely stable. The avg temp would be around 79.
Then i would try to keep your specific gravity stable at about 1.025 or 1.026. And if your measuring based on salinty 35. (Invest in a good refractometer and NOT a cheap hydrometer)
One of the fatest ways to fail in this hobby is using cheap testing and getting inaccurate readings.....
Once you get the basics down SLOWLY move forward.
REMEMBER THESES WORDS!! GO FAST YOU CRASH!! GO SLOW YOU GROW!!!

. Good luck!