Some basic learning that isn't easy to find:
Installing plugins and mods
How to make your own FTP file backup
How to make a your own database backup from the ACP
If you can't log in, out, or stay logged in, then you are having login issues, caused by cookies.
The most common reason is that we moved over your domain name but did not change your cookie settings yet. You can do it, or I can do it, it only takes a moment or two. If you have a domain name and you have not told me about it, even if you changed the name servers (see moving), you need to tell me so I can complete the process on my end. If your domain name looks like doggieRPG.sunwolves.com or sunwolves.com/doggieRPG, then this is most likely not the issue as these values are always populated correctly during your MyBB installation, so you should contact me so that we can investigate.
If you have your own domain name, say, DoggieRPG.com, and you want to use it, you need to edit these values. I'm using the example above of DoggieRPG.com (this is the same as http://www.doggierpg.com and http://doggierpg.com ), so you will need to use what applies to you.
$settings['bburl'] = "http://www.DoggieRPG.com";
Another, but unlikely situation is that your member clicked a link that lead them back to your old home where they are not logged in anymore. Simply ask them what the URL of the webpage is to verify.
If it is not either of those issues, and if you are using a URL like websitename.sunwolves.com, try having them use sunwolves.com/websitename (or vice versa).
In the extremely rare situation that the problem persists, have them clear the browser cookies that pertain to your website by removing any cookies that match a search for [websitename] or "sunwolves"
If registration emails aren't sending or something of that sort, it's likely you need to adjust your email settings in your ACP.
Go to ACP > Configuration > Site Details
Next, under ACP > Configuration > Mail Settings
This is a list of guides that I personally thought would be most useful. There are many guides out there, don't be afraid to look for more!