Newbie Healer in Frontline

Based on my achievements, I can tell that I took part in 66 frontline matches, and I didn't win most of them. Of course in a 1vs1vs1 game, its logical to loose most matches, but I didn't score 22 victories. I only have 11.

Based on this, I see that I'm really bad at PvP, and based on my tendencies/preferences, I figured I should stop using DPS jobs and just go for WHM (my main job), but I still have trouble figuring out all the little things... I guess I should stick with my team members, but when do I use my Adrenaline move?

Also, are there specific things that impact how I should play to get good? The modes where I'm most interested in winning are: Seal Rock (Seize) and The Fields of Glory (Shatter).

I'd appreciate any tips that I could get. Thank you

Adrenaline move to heal multiple allies that have lost HP that won't be easily covered by rapture regens. Worth mentioning also good to use if multiple people in your party get hit by range LB, range lb applies healing reduction, but Healer LB ignores this debuff. It's mana efficient to use it as a result in circumstances like these examples.

Healing in this game probably more than any other role comes with experience, you just have to play a lot of games. Onsal healing is a bit more important than Shatter for example, where there's less skirmishes and more making sure you help your DPS by glaring the ices and keeping miseries. Seal Rock you'll help with DPS in mid on the adds, and then support your party with base control.

In PvE as a healer you want to minimize healing GCD usage and maximize damage uptime. On WHM, this concept in PvP is similar in some scenarios, but you are a healer first and people take more damage and more regularly, so make sure you drop some old PvP habits and prepare for some good old fashion healing. However you'll want assists and any kills you can snipe to build battle high; so don't forget to use free gcds on glare and dump your miseries everytime you have a blood lily.

The best discord for frontline tips and to ask for help, advice or even people to play with is probably Revival Wings - https://discord.gg/wWrnBcM (invite code)
Brian Ricardo also plays with viewers when he streams so it's also worth playing some games with him when he's doing Frontlines - https://www.twitch.tv/brianricardo

For FL, make sure you are actively observing the situation. This sounds obvious, but new healers have a problem of focusing too much on the vitals to the side of their screen; helpful, but doesn't tell the story. For example, tanks and melee who are diving at 50% HP deserve your attention more than a ranged DPS at 25% HP behind you. The process of triage and priority is not new to healing in FFXIV, though the economics of warfare and the outcome of where your attention lies will change. For instance, supporting someone diving into the backline of the enemy team can mean winning an engagement at a critical point of the map, leading to a rout or allowing your team to rotate elsewhere. Meanwhile letting that target die to prioritize someone who needed that healing less critically may just lead to a prolonged encounter, so it can have pretty vivid ramifications.

Needless to say, Temperance, Dia, Glare, and Afflatus Misery, and to an extent Assize, can all be combined into a rather large burst sequence which can be modified based on what you have available or what you may need momentarily. Taking down a third of someone's healthbar isn't bad a for a healer, though Temperance has a pretty substantial defensive benefit so use discretion.