COVID bike build 2020 first timer
Before you commit to putting money and effort into a build ask yourself is this really the bike you want? Doing your own bike build can be fun and fulfilling but you want to end up with a bike you actually want and will enjoy riding

Is the frame actually the right size for you. You obviously can't sit on it do try it out in its current condition. What size is it and how tall are you? How tall is your neighbor? Look on Scott's web site for size guidance perhaps. Is the cockpit geometry right for you? The CR1 probably has a fairly aggressive low handlebar position. I note that the steerer is cut so you cannot raise the stem. What I would do in your position is measure the CR1's stack and reach geometry, then compare that with some other road bikes that you can test ride at local bike stores. That's not really an option during the current situation.

You also need to address safety issues. If the bike was owned by a pro it probably has done a lot of miles. There may be a reason it ended up in the trash (carbon is cracked) or perhaps your neighbor is getting a new bike for free or for a good deal an could not be bothered to sell this frame and get a couple of hundred bucks (if that) for it. Check the frame and fork carefully all over for signs of damage, impacts, paint cracks etc. Same for the seatpost, stem, handlebar. Take the fork out and inspect the steerer tube as well.

Check the wheels are true, check spoke tension by pinching pairs of spokes together - you are looking for ones that are loose. Check the wear on the brake track (there should be a wear indicator groove. Check the rims for dings or scrapes.

if the bike has lot of miles the the bearings may be worn out. Turn the bars and check for play, excessive friction, roughness or 'notchiness', do the same with the wheel axles. Put a finger in the BB bearings and turn them them looking for the same issues. 

Next step is to do your homework and start learning all about bike components and compatibility and how to install everything properly and all the tools you'll need. There are lots of resources online that are not hard to find with Google. My personal favourite is Park Tool which as has tons of great repair articles and videos. You should be able to find some full bike build up videos on YouTube which will get you started. If you have a particular problem or issue look for existing questions with answers on this site. Be aware that in component installation and adjustment details are really important. Do stuff right, don't take shortcuts.  

The good news is that road bikes are pretty standardized. A Shimano rim brake groupset will probably bolt right on. There are only a few options to deal with such as the front derailleur mount type and the bottom bracket type.

There are many online bike component stores the are easy to find via Google. I'd go with a bike specific store rather than Amazon etc. as you get better guidance and access to specs and data. Ebay is great for used parts but you do have to know what you are looking for.