To get started, you can either:

1. Go to https://generate.architectury.dev and download it as a Gradle project, there should be options for Architectury API, package names, etc.

Basically, follow their instructions according to Fabric/Loom, with the exception that the Parchment repository block is placed in allprojects…

allprojects {
    apply plugin: "java"
    apply plugin: "architectury-plugin"
    apply plugin: "maven-publish"
 
    archivesBaseName = rootProject.archives_base_name
    version = rootProject.mod_version
    group = rootProject.maven_group
 
    repositories {
-       // Add repositories to retrieve artifacts from in here.
-       // You should only use this when depending on other mods because
-       // Loom adds the essential maven repositories to download Minecraft and libraries from automatically.
-       // See https://docs.gradle.org/current/userguide/declaring_repositories.html
-       // for more information about repositories.
+       maven {
+           name = 'ParchmentMC'
+           url = 'https://maven.parchmentmc.org'
+       }
    }

… and the mappings dependency in subprojects:

subprojects {
    apply plugin: "dev.architectury.loom"
 
    loom {
        silentMojangMappingsLicense()
    }
 
    dependencies {
        minecraft "com.mojang:minecraft:${rootProject.minecraft_version}"
        // The following line declares the mojmap mappings, you may use other mappings as well
-       mappings loom.officialMojangMappings()
+       // Use mojmap with ParchmentMC
+		mappings loom.layered() {
+           officialMojangMappings()
+           parchment("org.parchmentmc.data:parchment-${rootProject.minecraft_version}:@PARCHMENTMC_MAPPINGS_YY.MM.DD@zip")
+       }
-       // The following line declares the yarn mappings you may select this one as well.
-       // mappings "net.fabricmc:yarn:@YARN_MAPPINGS@:v2"
    }
}

This is all performed in the root build.gradle script.

You can learn about:

1. Additional gradle configurations for e.g. using libraries or depending on other mods;
2. The Loom build plugin, used as a replacement to ForgeGradle;
3. Get coding with the Architectury API; or
4. Head back to the top.