I am onsite and rather than work on taxes to pay later. Can I pay, download the software and use at will. Is that possible or should I get it from another sources?

Yes you can buy the Desktop CD/Download program.  Most of us recommend it over the Online version.  It has more features and advantages.

Buy here, https://turbotax.intuit.com/personal-taxes/cd-download/ 

Did you already start in the Online version?  You can move your return to the Desktop program without paying for online.

First download the .tax2018 file from the Online version,  
<a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/replies/3300420">https://ttlc.intuit.com/replies/3300420</a>

Then see, How to Switch to Desktop,
<a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/replies/3302260">https://ttlc.intuit.com/replies/3302260</a>

After you get the program installed the first thing to do before you open your tax return is to update the program and install any state programs you had.  So you first might need to start a fake return to be able to download the state program (go to FILE - New)

Then you just OPEN the .tax2018 file, go up to File-Open.  You don't import or transfer it.

Or do you need to Transfer from 2017 Online?  I can tell you 2 ways.