Drupal 6.x

Another simple question I hop. I think it's probably a template function but I don't know how to change it. Would appreciate some (simple) suggestions. :)

Hi,

I am a Drupal newb. Currently inherited a website from a non-profit. The website is built with Drupal 6. There are some warnings on updating some module. I downloaded the updated module but don't know how to upload it. Do I need to install Drupal on my local machine or is there anything I have to do before making some modification & upgrade on the site? Please advise.

Second question is I have no idea where and how to upload photos/files into the site as I have no idea where the site/default is. Please advise.

Thanks!
Bee-Bee

Running 6.26 and anyone can register an account and control everything on the site like a master admin. We are getting hit with a ton of spam content submissions and I'm not sure if it is an exploit or improper settings. Anonymous users don't have any access than to be able to see the site but an authenticated user can do anything. Is there any other hierarchy like super admin or a way to restrict user registration?

Or is this an exploit that spammers are taking advantage of?

please help, im lost with this:

Notice: Use of undefined constant browscap - assumed 'browscap' in C:\xampp\htdocs\website\sites\all\modules\mobile_switch\mobile_switch.module on line 2

I'm struggling with a site that someone else developed and don't really know what I'm doing.
I'm not even sure if it's still Drupal 6.
The problem is that each page has a different banner at the top. I could change it in html but can't see how to change them in Drupal. This is the code with a different image source for each page:

Hi guys,
I'm looking for a solution so that when users associate a node with a new node they are creating, the users can specify where in the body they can input the value of the associated node. So for example:

Node A currently exists
Node B is being created and Node A is associated with it
Somewhere in the body for Node B, the user can specify the location to embed Node A.

I'm not sure what's the best approach for this. In Wordpress I'd think of using shortcode. Any suggestions?

Thanks
Ryan