Re: I received my Combo Kit in , now what?
Welcome to the forum.
The #6/7 tells you the line size you will need for your reel either 6 wt or 7 wt. You are going to need backing on the reel, then line, then a leader and finally some tippet.
Backing connects the line to the reel. Backing can be made of Dacron or Micron. most reels will take 50 yards of backing. A fly shop can help you select the right backing and amount.
For a beginner there are really 2 line type to consider, weight forward, WF, and double taper, DT. WF has most of the lines weight in the first 25' feet and then tapers off for another 40'. DT weight on 2 tapered ends. Each casts different. I still prefer WF over DT line. To start get floating line. You can also use split shot to get your nymph down to the bottom.
Leader lengths come in 7.5', 9', 12' and 15'. I started out using 9' leaders. I usually use 5x-7x leader for trout. There is a good thread by Frank Whiton in FAQ > Fly Fishing Gear section and an excerpt from a Left Kreh book about leader in Fly Fishing Articles > Everything Else.
Frank has a great thread on tippet size in the FAQ > Fly Fishing Gear section.
I use RIO line, leader and tippet with good results. Scientific Angler and Cortland are both highly regarded brands.