I need a copy of the signature page for my 2018 returns. i see my return, but not the signature page.

If you have used a paid tax pro in the past a form 8879 would have been included but it is not used in a DIY program like TT.

The 2018 Form 1040 is now two half pages.  The printout of the Form 1040 combines both halves onto one page.  The signature block in on the top half of the page.

IRS Form 1040 - https://www.irs.gov/pub/irs-pdf/f1040.pdf

You only sign a mailed tax return.  e-filed returns use the pint that TT asks for before filing as your electronic signature.