There's a few ways to go about this:
1. Attaching Effects DirectlyIn the resource manager, double click on the visual resource, and navigate to the "Attachments" tab. Here you can attach effect resources to specific bones. If you have an effect resource selected in the resource manager, simply clicking the arrow button for one of the bones will "paste" it in.
2. Attaching Effects via StatusesThere's a behavior script for both characters and items that allows you to set a persistant, permanent status on a character, called GLO_SetStatusOnInit.
You could then simply place the effects within that status, like so:
data "StatusEffect" "RS3_FX_GP_Status_FireImmunity_Root_01,KeepRot"
The advantages of this method are that you can use effects with overlays (overlays don't really work when attached to bones directly), and also attach multiple effects to the same bone. The Attachments tab seems to be a "one effect per bone" sort of deal.
Additionally, you can set material resources via statuses. Here's an example of using a material resource directly:
data "MaterialType" "Overlay"
data "Material" "1e0f6cfb-7215-4237-bcc4-61c5af54eb5e"
data "MaterialApplyBody" "No"
data "MaterialApplyArmor" "No"
data "MaterialApplyWeapon" "Yes"
data "MaterialApplyNormalMap" "Yes"
These material properties can also interact with the status visual effect:
data "StatusEffect" "RS3_FX_GP_Status_HolyFire_01"
data "StatusEffectOverrideForItems" "RS3_FX_GP_Status_Item_HolyFire_01"
data "MaterialType" "FadingOverlay"
data "MaterialApplyBody" "Yes"
data "MaterialApplyArmor" "Yes"
data "MaterialApplyWeapon" "No"
data "MaterialApplyNormalMap" "No"
data "MaterialFadeAmount" "2000"
2b. Alternative to the Status ScriptIf attaching a script to handle the status isn't feasible, an alternative idea is to place the status on a piece of equipment, and then equipping that to the character:
new entry "ARM_MyMod_FireEffectPlaceholder"
type "Armor"
using "_Amulets"
data "Act part" "0"
data "Magic Armor Value" "0"
data "DurabilityDegradeSpeed" "0"
data "Value" "0"
data "Weight" "0"
data "ExtraProperties" "SELF:ONEQUIP:MYMOD_FIRE_EFFECT"