There are many posts that are made daily in this sub with mod conflicts, game glitches and other problems that are entirely caused by trying to mod the game manually. CKAN is a program that was created to help you out exactly in this situation. You just select the mods you want, and CKAN handles installation, dependencies, and prevents conflicts!
For comparison, if you take about 30 minutes to install mods manually, in CKAN you'll take 5. If you mod manually, you get to know conflicts AFTER you boot up the game, and many times the conflicts are not easy to understand. In CKAN, that doesn't happen, because you can only install mods that are compatible with each other.
So, new players, do yourselves a favor: Use CKAN. It has been tested and refined by this community for years, and it just works.
Quick extra tip: There are also modpacks available for CKAN which make installing mods even easier, such as this pack that makes the game pretty with no extra complexities, and many, many others. One click, one install, and your game is ready. It makes your lives easier, and stops unnecessary issues from arising.