IPA first brew

[NOSNOWBrewing]

Hey everyone.
Today I did my first brew it's an IPA from a brewery. I started with 6 gal and did the whole thing right as far as I know I cooled the wort down to about 75-80 degrees (F) but there was a lot of the grain at the bottom of the pot I didn't put that into the fermenter and lost about a gallon or so with that. So should I of put that in the fermenter or did I do the right thing by not putting it in there? And doing the dry hopping do I just add it to the primary fermentation or do it in the second fermentation? Really basic question I bet I could of found it on here or on the web but I like to here from people that started like me.
Thanks best of luck to all
NOSNOWBREWING

 

[fartinmartin]

My last brew (Wednesday) after the boil and cool I had three litres of trub that did not go into the FV .
Re dry hopping , put them in a weighted sanitised bag so they sink after four or five days when it's calmed down, still in primary, that's the only time the lid has to come off before bottling day, unless you are a yeast washer, if you are a yeast washer saver rack and dry hop in secondary.