You can now start downloading and adding all the awesome mods that make Skyrim the best it can be by simply finding the mods you want on NexusMods and downloading them with the Vortex mod manager. You will run your game from the SKSE64.exe from now on. Or Download Here [follow instructions on that Nexus page. You can download this from the Skyrim SE Dashboard page on Vortex once you have it and have added Skyrim SE to your list. This is a must have and also a requirement for many mods basically it allows mods to do more complex things within Skyrim using scripts.
Download Vortex [then add your Skyrim SE to Vortex. Vortex is your mod manager I use this as i find it the fastest and easiest way to install most mods automatically without having to manually drag and drop tons of files. Firstly you will need an account at NexusMods [set that up go premium or don't you can get all the mods for free but downloads will be slower for non-premium accounts.