slideshow won't play in photo.only shows first picture

You have moments in photo,but if you click events, you have albums,which are easier for me to use.

So you are using the folder "iPhoto Events" with the fake events - albums derived from your iPhoto events?

To be able to make a longer playlist for the slideshow you have to create a slideshow project: select the photos in your album, then use "File > New Slideshow".

Now you can add click more songs from your music library to the list of "Selected Music" by clicking on them.

I have tried all variations of screenings,but nothing works!

What exactly have you tried already?

Does a slideshow project play correctly, if you select the photos in the album and use the command "File > New Slideshow"?

Does the problem only happen in your current photos library, or in any Photos Library? To test with a different Photos Library see this help page: https://help.apple.com/photos/mac/1.0/?lang=en#/pht6d60b524

Create a new photo library

• If Photos is open, choose Photos > Quit Photos.
• Hold down the Option key and double-click the Photos icon in the Applications folder (or click the Photos icon in the Dock) to open Photos.
• In the Choose Library dialog, click Create New.
• Type a library name and choose a location to store the library.
• Click OK.

Switch between photo libraries

• If Photos is open, choose Photos > Quit Photos.
• Hold down the Option key and double-click the Photos icon in the Applications folder (or click the Photos icon in the Dock) to open Photos.
• In the Choose Library dialog, do one of the following:
• Click the library you want to use, then click Choose Library.
• If the library you want doesn’t appear in the Choose Library dialog, click Other Library, navigate to the location of the library, select it, then click Choose Library.

Is your Photos Library an iCloud Photo Library, or are your photos stored locally on your Mac?

If the slideshows do not play only in your current Photos Library, but play well in a differnet Photos Library, try to repair the library as described here: https://help.apple.com/photos/mac/1.0/?lang=en#/pht6be18f93

Important: You should back up your photo library before repairing your library.

• If Photos is open, choose Photos > Quit Photos.
• Press Option-Command and double-click the Photos icon in the Applications folder (or click the Photos icon in the Dock).The Repair Library window opens.
• Click Repair to rebuild your photo library.

However,I found you have to click on an Event,then slideshow.

There are no events in Photos - only moment, collections, years, albums.

To play an instant slideshow, you have to select a moment or a collection: https://help.apple.com/photos/mac/1.0/?lang=en#/pht56eafa987

Play an instant slideshow

You can quickly play a slideshow of the photos in a collection or a moment. You can select a theme and music for the slideshow, but you can’t customize the slideshow further.

As to the music:

Can anybody tell me how to select more than one iTunes,in photo?The old system allowed you to drag and select as many as you want.

In Photos you add the music to the slideshow by clicking the song - you do not drag them to the playlist. This will work in a slideshow project: https://help.apple.com/photos/mac/1.0/?lang=en#/phtae8c6d40

To select music for the slideshow, click the Music button , click the down arrow next to Music Picker, then select a song or songs.