Keep your bass on it's back and do not take off all of your strings at once. Without tension, your soundpost will fall.
Make sure you keep a very close eye on your bridge- it can and will move as you tighten your strings. Most commonly it will bend towards the finger board as you tighten the strings. To avoid having to go back and loosen them when you are done, just firmly grab either side of the bridge and push down steadily if you notice that it is starting to lean towards the finger board.
To anchor in the string, just push the string into the correct hole of the peg box to where there is a little under an inch sticking out on the other side. The easiest way to do this is to stick it in and start to turn the tuner, but make sure you are going in the right direction or you will have to take it off.
If you don't have a string winder, changing strings can be physically painful. I recommend buying one they are around 10 and save tons of time. Some people (to save time) stick the string a few inches into the hole in the peg box, then wrap the end that they just stuck through the hole around the top part of the string, then simply wind it. That was oddly hard to explain with words, but if you try it out it will make more sense. It doesn't look as neat in the peg box but it saves tons of time.
As for loosening strings, you will find that you will have to loosen certain strings to have access to others. Just don't take them all off at once.
Oh! And when you feed the string through the tailpiece, be positive that the ball is allll the way pulled up in the tailpiece.
You will develop your own method for changing your strings, no doubt. Be sure that you have plenty of time for your first try.
Sorry, that was a novel! Have fun with the solo strings!
