I have purchased and downloaded Turbo Tax Premiere 2018. I have filed one tax return and would like to start another....having troubles, any ideas?

You are asking from TT premier online (web), not the download version.

TT Online is only good for one return per account.

for $128.00+ there is only one return per account?

Go to file, hit drop down menu, select New Return option

There is no file option