To familiarize yourself with CurseGradle, please read the project's official wiki.

Note: in recent versions, it seems that the changes outlined in this article are not necessary and perhaps even harmful.

(Note: Last updated for Loom 0.2.5.)

The additions necessary for usage with Fabric have been highlighted in green. If you are using Loom 0.2.5 remapJar.output should be just remapJar instead.

They are, in order:

• afterEvaluate { ... } - Loom's remapJar tweaks currently happen after evaluation, and as such remapJar.output can only be read then,
• mainArtifact(remapJar) (or mainArtifact(remapJar.output) for Loom 0.2.4 and earlier) - the primary artifact submitted to CurseForge should be the output of remapJar, that is the remapped (production-ready) mod .JAR file,
• uploadTask.dependsOn(remapJar) - make sure that the CurseForge upload task only runs once the remapped JAR has been built,
• forgeGradleIntegration = false - as you're not using ForgeGradle, that specific integration has to be disabled.

You can set Modloader to Fabric and add supported Java versions with addGameVersion.

addGameVersion "Fabric" //Set Modloader to Fabric
addGameVersion "Java 8"
addGameVersion "Java 11"