Install Optifine into MultiMC instance on Linux workstation

install-optifine.sh

#!/bin/bash

MULTIMCDIR=/home/cnaude/Minecraft/MultiMC

if [[ -z "$2" ]]; then
  echo "** Usage: $0 [Optifine.jar] [instance]"
  exit 1
fi
FILE=$1
if [ ! -e "$FILE" ]; then
  echo "** Unable to read $FILE"
  exit 1
fi
JARFILE=$(basename $FILE)
VERSION=$(echo $JARFILE | sed 's/OptiFine_//g' | sed 's/.jar//g')
NEWJAR="OptiFine-${VERSION}.jar"
MCVERSION=$(echo $VERSION | sed 's/OptiFine_//g'| sed 's/_.*//g')
INSTANCE=$2
INSTANCEDIR=${MULTIMCDIR}/instances/${INSTANCE}
PATCHESDIR=${INSTANCEDIR}/patches
LWVERSION=1.12

LIBDIR=${MULTIMCDIR}/libraries/optifine/OptiFine/${VERSION}
if [[ ! -d $LIBDIR ]]; then
  mkdir -p $LIBDIR 
fi
cp $FILE $LIBDIR/$NEWJAR
if [[ $? -eq 0 ]]; then
  echo "** Copied ${FILE} to ${LIBDIR}/${NEWJAR}"
fi
if [[ ! -d $INSTANCEDIR ]]; then
  echo "** Unable to find ${INSTANCEDIR}"
  echo 1
fi
if [[ ! -d $PATCHESDIR ]]; then
  mkdir -p $PATCHESDIR
fi
cat <<JSON > ${INSTANCEDIR}/patches/optifine.json
{
    "+libraries": [
        {
            "name": "net.minecraft:launchwrapper:${LWVERSION}"
        },
        {
            "name": "optifine:OptiFine:${VERSION}",
            "MMC-hint": "local"
        }
    ],
    "+tweakers": [ "optifine.OptiFineTweaker" ],
    "fileId": "optifine.OptiFine",
    "mainClass": "net.minecraft.launchwrapper.Launch",
    "mcVersion": "${MCVERSION}",
    "name": "OptiFine",
    "order": 200,
    "version": "${VERSION}"
}
JSON
if [ $? -eq 0 ]; then
  echo "** Created ${INSTANCEDIR}/patches/optifine.json"
fi

so what do i do with this???