This one is primarily for DPS players, but for all raiders a parsing program is a much needed to add on for the game. It is important to know where your dps is, and I strongly recommend dummy parsing before getting into serious hard mode operations. Parsing programs are excellent for tanks and healers as well. Healers should know how well they are doing and should focus on their "effective heals". Healing someone at 100% does not help a raid team, though the healer may feel like they are doing quite a bit. The utility for tanks is endless. Most of the timers for mechanics in these parsing programs will help time defensive abilities or help you know when a move or tank swap for a mechanic.
There are 2 main options I have come across for parsing programs.
http://www.ixparse.com/ - Starparse - easily the most used and preferred in the game.
https://www.microsoft.com/store/productId/9P63T6ZQMHBZ - Old Republic Battle Parser (Orbs) in the Microsoft Store - My personal preference and what I would recommend. 10/10
Both have their strong points. Starparse seems less supported and more dated, but was the main stream parsing program for many years. Old Republic Battle Parser is newer and comes standard with many timers that one would have to manually enter into star parse. I find the overlays far superior to Starparse.
Old Republic Battle Parser has some very nice added features, such as the floor overlay for IP-CPT and an interrupt tracker. I generally find that the Old Republic Battle Parser runs better on my system, but I do like starparse for its damage type recaps. No reason you cannot use both.
Both of these can report parses to Parsely - SWTOR Combat Log Viewer, which is my go-to for analyzing my raid team's performance.
Once you've downloaded your chosen parsing program, there are some in-game settings that need enabled. Go through preferences > Combat Logging and enable logging to file.
Sometimes the game will need to be restarted if the parsing program doesn't immediately work. I recommend doing this for your first run of it.
For Starparse only, you will need to make sure that the directory is set so that starparse knows where the files are located. Orbs does this for you.
Open Starparse and to to FILE > Settings. Under the General Tab, make sure the Log Directory is set to where the Star Wars Combat Logs are kept on your PC. This is usually Users\YOUR NAME\Documents\Star Wars - The Old Republic\CombatLogs. You'll notice mine was set up a little differently
Click the "Parsing" button on the top right side. It should turn green. If it turns yellow, Attack something and see if it turns green after that.
For more help with StarParse - Troubleshooting | Ixale's StarParse | Next-Gen SWTOR Parser (ixparse.com)
For More help with Orbs - https://drive.google.com/drive/folders/10W87VTUGUsICkNqpyMrPSRRfXcbjkJkS?usp=sharing