In my opinion, shot placement far outweighs caliber when it comes to what bullet. I use a 6.5 PRC to hunt big game all the way up to moose/grizzly bear because I have a lot of confidence I can place the bullet exactly where I want. I would say your 6.5 Creedmoor is more than adequate.

Search elk vital pictures so you know where to aim based on how the animal is standing.

You'll want some binoculars. Don't have to go crazy expensive as new hunter, especially if hunting cow elk where you won't be judging antler size/legality across a far distance.

A range finder can help you determine if your target is within range. If I were helping out a new hunter, I'd encourage them to keep their shots within about 250 yards or so. The biggest things to help your accuracy are, practice before you go. Get confident. Then, in the field, get a solid rest when shooting vs shooting "off hand". Shooting off hand can be difficult even at short distances.

Use warm clothes/layers, you probably already have some. Camo patterns are not needed. A lot of cow elk hunts are late season/cold weather/snow.

Watch some videos on field processing. I especially like the "gutless method". You'll struggle at first, but get better with each harvest until it comes easy. You'll want some game bags to hold the meat.

As far as having high quality meat. I've found the best thing to be get the hide off quickly and let the meat cool. Keep it cool/dry. If processing your own meat, remove all fat and as much silver skin as possible. Freezing or cooking with those still in the meat will give a strong 'gamey taste.