Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
Start up disk means your internal storage or hard drive.
To free up space, you have to delete unwanted files, applications, music, movies etc and then empty the trash.
First let's check what is taking up all the space. For that we're going to use an application named OmniDiskSweeper.
Download Omni Disksweeper from here--> https://www.omnigroup.com/more
Use the trial or free version. That application will show the large files that are using the space of your hard drive. So you have to find and remove those unwanted big files that you are not using and empty the trash.
DO NOT delete any system files from System, Library, Private folders etc. If you delete any system files, your Mac will not boot or load. Only delete files which are in your home folder.
Scan with OmniDiskSweeper and it will give you an idea of what is taking up space. It will show large files and its location. Note it down.
Then in Finder, click on GO menu at the top and select Home. This will take you to the home folder. Open each folder and delete unwanted files from there and empty the Trash.
DO NOT trash iPhoto Library, Photos Library or iTunes Library.
Make sure you empty the trash after deleting unwanted files and stuffs. Remember, to free start up disk, you must delete some old files. If you get an external hard drive, then we can move the files to that drive and free up space on internal storage.
If you have any difficulty on following the steps above, please let me know and I will walk you through it.
Click Download next to OmniDiskSweeper or click this Direct download link --> http://downloads.omnigroup.com/software/MacOSX/10.8/OmniDiskSweeper-1.9.dmg
It is a small file and will be downloaded instantly. So check your Downloads folder for a OmniDiskSweeper-1.9.dmg file
Follow the steps below to start secure remote support session.
If you are talking to me from your Mac now, then just click this link ->
Follow the onscreen instructions to connect. An application named Citrix Online Launcher will be downloaded. Then open the Citrix Online Launcher file you see there and then open the Citrix Online Launcher application. You can also open it from Downloads. Open Citrix Online Launcher file. Allow permission to connect or Join session if asked.
(If you don't seethe downloaded Citrix Online Launcher file, then click on the Finder icon on dock, then click on Go menu at the top of the screen and select Downloads. This will bring Downloads folder. Now you see a file named "Citrix Online Launcher.dmg" file there. Double click on it to open. Then open the blue citrix online launcher icon)
Let me know if you have any difficulty connecting to me.
What error are you getting ?
When you get the external hard drive, please post a reply in here. Then I will connect to your Mac and we can fix Photos app.