Step $1$: Use the search function on FRED to try and find the series that you think come closest to the ideal measures you identified in part $($a$).$ I wound up working with the following three series

$$Employment Level $-$ Bachelor$$s Degree and Higher, $25$ Yrs$.$ & Over$($LNS$12027662)$

$$Population Level $-25-54$ Yrs$.($LNU$00000060)$

$$Population Level $-55$ Yrs$.$ & Over$($LNU$00024230)$

Since we$$ve restricted our wage series to individuals $25$ years and over, it makes sense to do the same thing for the employment and population series. Unfortunately, FRED does not appear to have a series for $"25$ and over". However, it has two separate series for ages $25-54$ and $55$ and over$.$ So adding these two series should give us the denominator we want. If you think that other series are more appropriate, that$$s totally fine, as long as you discuss why in part $($a$)$ above.

Step $2$: Using similar steps as in Part $1,$ compute the number of employed college graduates $(25$ years and older$)$ as a fraction of the population aged $25$ and older, using a formula like this: $100*($a$/($b$+$c$)),$ where a$=$"college educated workers", b$=$"workers aged $25-54",$ and c$=$"workers aged $55+".$ Like in Part $1,$ the series should already be in percent, which is what we want, so there is no need to change the units.