I am having difficulty connecting with any brokerages. It may be a problem between TT and my Internet Explorer. How do I get TT to use Firefox instead both are laptop

Not sure if it is as simple as this - but I have Chrome as my default browser, so TT used Chrome for me.  Close TT, then open Firefox and check your settings.  If it isn't your default browser, make it your default (sorry, I don't have Firefox so not sure exactly how you would do that, but there must be a Settings or Tools/Settings option in Firefox).