I dont really understand this explanation, is there a simpler way to calculate sfr’s for a given maturity?

No.

Hey there Lloyd !

Give this a go. It helped me.

CFA Level II: Derivatives - Pricing and Valuation of Swaps -Part I (of 15) - YouTube

the problem asks you to calculate the swap spread, which is the difference between the fixed rate and the spot rate. for a non-deferred swap, the fixed rate lasting for t years is given by

SWAP = ( 1 - Pt ) / ( P_{1} + P_{2} + … + Pt)

where P_{t} is the price of a t-year zero-coupon bond

in this case, SWAP = (1 - .8396) / (.9615 + .9070 + .8396) = .059229718

the spot rate for 3 years is already given to be 5.25% or .0525

therefore, the swap *spread* is SWAP - spot rate = .059229718 - .0525 = .006729718 or .673%

the formula for the swap should be somewhere in your cfa notes. memorize it.