Hi, Fred: having the tone arm horizontal with the surface of a typical 140-150g LP is a good starting point. The tracking force (VTF) should be set in the middle of the recommended range and yes, use the centerline of the tone arm tube for sighting. If the stylus was correctly attached to the cantilever by the manufacturer, you'll be close to the desired stylus rake angle.
If you do a search here at Audiogon for "SRA" you'll find all kinds of information, and lengthy debates about how to set it. The reason for paying attention to SRA is that when the record is made, the cutting head is drawn through the vinyl at a forward angle so the waste material from cutting the vinyl is pushed up out of the groove. By setting correct SRA to replicate the cutting head angle, the sides of the stylus will correctly contact the walls of the groove and you'll get better sound. Vertical tracking angle (VTA) has been the common term used for cartridge alignment but SRA seems to be gaining acceptance as the more accurate and useful parameter. Again, a search will provide plenty of reading material.
But, it can get complicated in a hurry. Records are different thicknesses so if you set SRA for one range of record thicknesses it won't the the optimal SRA for thicker or thinner records. Some people change tone arm height to adjust SRA for each LP. Plus, the SRA is affected by VTF. Decrease VTF and the tone arm rises as the cantilever suspension relaxes and SRA increases. Conversely, increase VTF and the tone arm lowers as the cantilever suspension compresses and SRA decreases. But, the change in SRA with increasing or decreasing VTF is compounded because changing VTF also changes how the cantilever aligns with the cartridge body and how the cantilever generates the signal within the cartridge.
"Sheesh, I just wanted to play some records!"
Keep it simple for now. By setting the tone arm at horizontal using the mid-range of recommended VTF on a mid-range thickness LP you'll be close for most LPs. The SRA won't be ideal for thicker or thinner vinyl but it won't be that far off. You can experiment by raising the tone arm to increase SRA or lowering the tone arm to decrease SRA to see if you find the "sweet spot" for your cartridge and stylus.
Or just play some records. '-)