Good advice below, but don’t feel like everything has to be perfect or that you need to master every feature at once.
Begin with the basics—biographical details, sources, etc.—and then build on that foundation.
Remember, this is a collaborative site. If something is missed, you can always go back later, or someone else might step in to improve it. The beauty of this system is that we are all working together to enhance the same profile, rather than each generation starting from scratch.