Welcome Darren. You'll want to leave the hop sack in the fermenter the entire time. One option, when you bottle, is to use a pair of sanitized tongs to quickly remove the hop sack, and then put the lid back on. A better option is to cold crash, after ensuring the hop sack is at the back of the LBK. See my post regarding cold crashing.
Also, for best results, follow the 3-4 rule. 3 weeks in the fermenter, 4 weeks in bottles. When fermenting, ideally you don't want the beer to get warmer than the high 60s, mid 60s is better. After bottling, keep the bottles at 70 or low to mid 70s for 4 weeks, then refrigerate for at least 3 days before drinking. Again, read some of the posts listed in my signature.