Made it so the app actually start

code/src/app/src/main/AndroidManifest.xml

@@ -8,6 +8,14 @@
         android:label="@string/app_name"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
-        android:theme="@style/Theme.Fitbot" />
+        android:theme="@style/Theme.Fitbot">
 
+        <activity android:name=".MainActivity"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+        </activity>
+    </application>
 </manifest>

code/src/app/src/main/java/com/fitbot/fitbot/MainActivity.java

@@ -1,4 +1,13 @@
 package com.fitbot.fitbot;
 
-public class MainActivity {
+import android.os.Bundle;
+import androidx.appcompat.app.AppCompatActivity;
+
+public class MainActivity extends AppCompatActivity {
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.testlayout); // replace with your layout file
+
+    }
 }

code/src/app/src/main/res/layout/testlayout.xml

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <TextView
+        android:id="@+id/testText"
+        android:layout_width="200dp"
+        android:layout_height="100dp"
+        android:text="awa"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.497"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintVertical_bias="0.465" />
+
+    <androidx.constraintlayout.widget.Guideline
+        android:id="@+id/guideline2"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        app:layout_constraintGuide_begin="20dp" />
+</androidx.constraintlayout.widget.ConstraintLayout>