Benefits are listed on the UA website. CPU (Complimentary Premier Upgrade) requested/waitlist is complimentary/automatic with most domestic ticket purchases (and award tickets if holding certain UA credit cards) except for Basic Economy tickets and will display on your itinerary on the website as below. Unsure if “premium transcon" routes (LAX/SFO-EWR) are CPU eligible, I believe they are not. SNA-EWR (if available) might be CPU eligible (possibly to domestic 1st, not lay flat). CPU can clear at any time as per the timeframes listed on the website. Upgrade list in priority order is easily viewable on the app or website on flight status pages.

Realistically speaking, as a Silver, your chances for a CPU are slim to none and with all due respect as the expression goes, slim just left town. As a LT Gold Million Miler, for ~15 flights this year (LGA/ORD/DEN/SLC) I’ve cleared 0 (zero) CPUs and averaged #10-15 on a list of 25-40 eligible for a fully booked 1st class cabin of 8-16 seats. Last year IIRC I got 1 or 2 CPUs in ~20 eligible flights.

Congratulations on your new status. Main benefits to me are free checked bags (and skis) and being able to select complimentary Economy Plus Seats. (I recommend emergency exit row window as the safest economy cabin seat.) Not as sweet as 1K or GS but better than bupkis.