There are several types of upgrade and it is always best to ask the Project Administrator which upgrade would best help you achieve your goals. Upgrades may involve testing more STR markers (e.g. going from 37 markers to 67 markers) or SNP testing (either with the Big Y or a SNP Pack). Alternatively, you may want to add an entirely different test to your kit (e.g. Family Finder).
Upgrading your STR Markers
If you wish to upgrade from 12 or 25 markers to 37 markers or higher, just click on the blue Upgrade button on your FTDNA Homepage and then click on the appropriate Upgrade Price button on the right and follow the instructions ($99 for upgrading to Y-DNA-37 from Y-DNA-12).
You can also upgrade to 67 or 111 markers. This can be useful to delineate the finer branches the Mutation History Tree associated with your particular subgroup. It can also give a more precise estimate of when the common ancestor shared by two people lived (+/- 200 years). It may at times be advisable in certain other specific circumstances, but please seek advice from the Admin if you are thinking about doing so, because there are new tests becoming available all the time (in particular, SNP testing) and some of these new tests may be more informative for you than an upgrade to 67 or 111 markers.
Upgrading to a SNP Test
If you want to order the Big Y test, click on the blue UPGRADE button, and then click on the blue button beside the Big Y test. This is the most expensive of the DNA tests and usually costs $575. But it can be reduced to as low as $400 in the frequent sales that FTDNA have during the year.
If you want to order a SNP Pack or a single SNP test, again click on the blue UPGRADE button, and scroll down to the ADVANCED TESTS box. Click on the blue BUY NOW button then select SNP PACK from the dropdown menu (or search for the single SNP you want). Again, the Project Administrator can advise you on what test is best placed to address the question you want answered. And if all this gets too confusing, simply ask the Admin to order the test you want ... so that all you have to do is simply click on the green PROCEED TO CHECKOUT button and pay for it.