Congrats on the new bass. But remember, they say, upright bass and trumpet are the hardest instruments to play consistently well, physically. So, in other words it's a commitment. Most bass players who buy and start playing upright quit trying and let the instrument gather dust in a corner within 6-months and sell the bass within 2-years. Why? Cause it ain't easy to get good at.
1) 'Learn how to hold it.' You don't hold the bass while playing it. The shoulder of the bass leans into your lower chest/upper stomach area. Your fretting arm elbow is held close to 90-degrees from the body. Your plucking/bowing arm hangs straight down to pluck as close to the end of the fret board as possible.
2) Watch you posture while playing. Slightly bend both knees as if swing a bat or golf club. That 'sports stance' keeps the back straight, relaxing that area and less chance of muscle strain.
You can look at the two 'Bass Lessons to Costa Rica', I posted at
www.youtube.com/bassmickeyd where I talk about this.
3) Go slow practice in short spurts. 10-15-minutes, at a time, for the first month till you muscles and tendons get used to being used in a different way. Tendentious is a popular ailment amongst beginner and experienced upright bassist. You can do that 5/10-times a day. Just don't try to pack all your upright practice all at once.
You should use a pre-amp with between the Fishman pickup and your amp. Because the pickup is located so close to the strings the sound is more string sound and less body sound. A pre-amp smoothes that sound out. David Gage pickup is a better choice.