premiere elements 15 lagging

[lemedia]

So i bought a new macbook pro 13,3 retina display 2015 tech specs:

Processor: 2,7 GHz Intel Core i5

Ram: 8 GB 1867 MHz DDR3

graphics: Intel Iris Graphics 6100 1536 MB

But when i edit in premiere elements 15 the playback is laggy i know you can do a preview render but why do i have to do that because elements 15 requirements optimal performance says this:

Mac

Processor: 64-bit multicore Intel processor

OS: Mac OS X 10.9/10.10/10.11
RAM: 6GB

Hard Disk: 100 GB of available hard-disk space to install applications; additional 5GB to download content

Display resolution: 1920x1080

High speed internet

and i have all that so why is the playback laggy? i saw that in premiere pro you could increase your use of ram but i haven't found that option in elements 15.

please help!

[Bill Sprague]

What is the source of the footage?  How are you setting up the project?

[lemedia]

the footage is coming from a gopro hero 4 1080 p 60 frames and a nikon d5300 1080 p 60 frames i set up my project like this I start the program then i drag my footage from my harddrive in to premiere elements:)

[Peru Bob]

Did you render the timeline?

Are you using the media from an internal or external hard drive?

Use the GoPro utility and convert the footage to the CineForm codec ant then import into Premiere Elements.