Robin, you have a lot of questions on a very wide range of topics. This is perfectly normal when you're getting started here because WikiTree has so much stuff and there is a pretty significant learning curve. I recommend that we deal with these things one at a time instead of trying to do everything at once.
First, for any help with logging in, you need to write to info @ wikitree.com (without the spaces) and they will get any problems with your login name and password resolved.
WikiTree does not have such a thing as "my tree" or "your tree". It's all one single monster-size tree that has only one profile for any person and we all share the same tree. That means that any information you have about any of the profiles that are already here is very welcome and, as a member, you can add that information, although it is good to communicate (either by a comment on the profile or a private message) with the profile manager about any major changes before making them.
As to copyrights, they do not apply to information - facts cannot be copyrighted. If there is an image - either a photograph or a scanned document - then that can be copyrighted and you cannot add those on WikiTree unless you have permission of the copyright owner. You can, however, transcribe the documents to state the information here, but please do not quote long excerpts word-for-word without permission of the copyright owner. You can quote small pieces, though, as long as you make sure to attribute your quote to the proper source - this comes under the "fair use" laws.
After your login capability has been established and you begin working here, please ask any specific questions as they arise and you'll get prompt answers to anything here. Welcome to WikiTree!