Yeah, its actually really easy and painless as frumple says.
All you have to do is download the mod loader then install it. Once you do that it edits the game main menu so whenever you open terraria there are buttons to search for, download and finally activate whatever mods or combination of mods you want to use.
The major mods I am using are mostly the same as xaritscin, but with a few added utility and quality of life mods that make the game far less painful.
In order from most to least important:
Recipe browser, which lets you look through all the recipes in the game allowing you to search by ingredients, name and mod. It also shows you what enemies drop what items. It is super useful in figuring out what you need to build, and will mean that you don't need to check the 5 different wikis from every mod every 5 seconds.
Magic storage: A very useful item management system that will remove the need to have dozens of different chest all filled with random things as well as removing the need to spend 5 minutes searching through them all to find that one item you have in a chest somewhere but you just aren't quite sure which one.
Auto-trash, which lets you select items to auto trash instead of picking up so your inventory won't fill with random useless crap that there is literally 0 use for.
Bags of holding, which lets you craft bags that pick up items by type and store them in the bag instead of your inventory aslong as you have the bag in an accessory slot. Losing access to an accessory slot to use one is a pain, but the fact that with say, a mining bag your inventory won't fill up with 15 different ores, gems and stones its worth the tradeoff.
Helpful hotkeys which adds hotkeys for stuff like auto-placing a torch at the closest location to your cursor that it can, or a hotkey to toggle autopause on or off.
Fargo's mutant mod which adds an NPC that sells all the boss summons once you have already beaten the boss which is very useful for grinding the bosses (note his versions let you summon the bosses anywhere and as many at a time as you want to). The mod also adds lategame extremely powerful accessories that combine literally hundreds of accessories into single slots.
Omniswing, which makes all weapons have auto-swing/shoot as long as you are attacking so you don't have to click 100 times in a row.