ADVICE NEEDED - BIKE Build :)

1st post! Hi all, have ridden a 2010 Trek Alpha 1.5 since new but finally during lockdown decided to chop it in and build a new bike for me. Components (costsbelow for those interested. Big question I have though is around the bottom bracket, the frame has arrived with bearings set in place although every video I’ve seen has the crank empty to start with. One spins on drive side and one doesn’t. Question to the far better informed out there, a) what are they? b) do I need to remove/change them c) I have an RS500 BB coming for it that is allegedly compatible? Is this true! Thanks again!

Can’t attach image unfortunately. So it’s set as my profile pic.

spec;
Specialized Carbon Tarmac Sport SL2 £150
Ribble Sportiv Forks (£97)
Shimano 105 GS (£130)
Shimano 105 Crank (£65)
Look Pedals (£30)
Toseek Carbon Bars (£40)
Wheels (not yet purchased! Need recommendations under the £250 mark)
Rubber (as above)