Depends on what you mean by "tighten up the stock", the exact configuration, model and maker. Depends on what you mean by "tighten up the stock", the exact configuration, model and maker.
Your serial number indicates that your Marlin model 336W was made in the year 2009.
Best left to a gunsmith
WAL-MART
You should let a gunsmith do this.
1978
1977
2000
The way to put on a stock on a US. Army Alpha Black is by unscrewing the screw in the place to put the stock. Then when that is out you then put it where you won't loss it, then you slide on the stock with the hole on the stock on the bottom. When that is sled on you then use the tools that are in your magazine looking thingy; the one in the middle is the one you use to tighten it and loosen it. Put the tool on the screw to tighten or loosen it. To tighten is turn tool to the right; to loosen it turn tool to the left. Once you have that done you can shift the stock by pulling the lever and stock together and either push or pull it to suit you.
The BL (Big Loop) has a laminate stock, a large finger loop (for shooting with gloves), and a slightly shorter stock for shorter length of pull. The W has a walnut stock, which is a little less expensive than some of their other models. Its stock is also a little longer for a longer length of pull. For the same barrel length, the shorter overall length of the BL makes it my choice!
Best to let a gunsmith do it.
2005.