Before you do all of this i actually used 2 other micro sd cards that are at least 8gb or more just in case something got messed up and i still had the old sd cards that came with the solo. if you do mess up on you will just have to reformat the sd cards and start over for which ever device you messed up on. But this does work as long as you have no other issues with your controller or solo like the wifi card, or etc.
step one: is to remove the sd cards from the controller and the solo keep them separate so you know which one is which when you do this update.
step two go to this site
OpenSolo/documentation and follow all the steps so downloading 7 zip and win32 and follow all the other information on that page.
step three: this is where you get the solo sd card image for the solo and the controller,
OpenSolo/documentation scroll to the bottom and you will see
Open.Solo.3.0.0.CONTROLLER.SD.Card.Image.7z and
Open.Solo.3.0.0.COPTER.SD.Card.Image.7z download both of them it will take a little while. then when they are downloaded you need to unzip them so use 7zip by right clicking on each one of the files to where ever it download to when thats done then open up win32. When you have win32 open make sure you have the sd card in your computer you are going to use for the controller or solo and click the browse but to find the unzip file for which ever one you are updating first and open it then write it to the sd card, when it is finished do the same thing for the other sd.
step four: now you need to put the right sd cards in the controller and solo then put everything back together once done let both devices power on and do there thing after they cycle up turn them back off.
step five: Now this is where you will do a factory reset to both so on the controller with it off hold the power and fly button until you see updating on the screen,then let it do its thing do not rush it. Now on the solo turn it upside down take off the gimbal if you have the motorized one, then you will have to get a tooth pic and place it in the hole next to the pair button after you feel it push in then turn on the solo and keep holding the pair button you should see the orange light start flashing fast then you can let go. same thing do onot rush it let it do its update it will finish you should see lights changing soon and noises being made it took mine 20 minutes to update.
step six: now once both are updated for sure turn them both back off and then back on, then when they both boot up press the pair button on the solo until you see solo detected on the controller once you do press a and b at the same time and they will start paring. once they are paired you will have to calibrate the compass and level the drone there will be instrustions on what to do on your tablet to finish the process.
step seven: After all that you should be ready to fly and have fun.