script.ps1

$serviceName = "MyService"
if (Get-Service $serviceName -ErrorAction SilentlyContinue)
{
    $serviceToRemove = Get-WmiObject -Class Win32_Service -Filter "name='$serviceName'"
    $serviceToRemove.delete()
    "service removed"
}
else
{
    "service does not exists"
}

"installing service"

# current directory
$directorypath = Split-Path $MyInvocation.MyCommand.Path

$secpasswd = ConvertTo-SecureString "MyP@$$w0rd" -AsPlainText -Force
$mycreds = New-Object System.Management.Automation.PSCredential (".\MyUserName", $secpasswd)
# you need hardcode application name anyway
$binaryPath = $directorypath + "\ApplicationName.exe"
New-Service -name $serviceName -binaryPathName $binaryPath -displayName $serviceName -startupType Automatic -credential $mycreds

"installation completed"