Using Logic Analyzer for SPI
Remember that a logic analyzer is nothing more than a fast clocked comparator. What do comparators do? They compare a voltage! With a reference voltage. This is then clocked and at the clock the channel was measured if it was high or lower than the reference voltage.

So, You have two things to adjust. The clock, and the reference voltage.


Clock - How do you know your clock is fast enough? Keep sampling faster, if you see more and more "edges" then you know you need to run faster.
This applies for an unclocked signal, for a clocked signal like spi, its even easier. Since you know the data comes in groups (usually 8 bits at a time), all you have to do is find 8 rising edges and 8 falling edges. If it looks like the edges are being poorly sampled (ie there are only 5 or less samples between clocks) you will want to turn up the speed of your sampling, so you get more samples per clock.
Reference Voltage - You have to set the reference voltage at the correct level. Check your logic levels, if its 5V cmos, set it at 2V. 3.3V TTL = 1.25V (or thereabouts). 


A caveat to this is all logic analyzers have limited memory (except for the new 3000 series from tektronix and keysight, 20M of memory will buy you a lot of time, like almost infinity). So you can't usually sample the at the fastest speed because there is a trade-off of sampling speed vs how much time your total samples last.