What to do after installing marlin doesn't work?

I just installed marlin into the Arduino mega. I used 0023 as suggested by the printer kit maker (DIYTECHSHOP) And with the most up to date version of Arduino too. The compile and upload works but after the file is said to be installed into the Arduino nothing happens... When I turn on power the lcd just lights up with rows of full white block. I'm. It familier with this firmware thing but I feel so dumb for having absolutely no idea what to do next. I mean I don't expect it to just magically work after I wire it up and download the firm ware up but I feel like something should show up in the lcd...

did you unplug the arduino board from a power source?

Yes I did, but it was still attached to the RAMPS shield. Should I completely take it out?

ramps shield is fine to leave on.
do you see any flashing lights?
do you have it plugged in proper?
have you selected your board type from the Arduino IDE interface?
are you using the right COM port?

Yes all the lights flash properly flashing and the connections are all set properly too. I just uploaded a blink code with the built in led and it ran. So it doesn't seem to be the board.

Full blocks on an LCD like that can mean the display isn't configured in the firmware or the wrong display is selected. If the configuration is correct the display should show the default screen. If Marlin was installed without editing the display config this is the most probable reason. If the proper configuration is loaded and there are still issues the cabling to the display may be in the wrong connectors. The display and the adapter on the RAMPS should have an A and B label, they need to match on each end.

I switched up the connections which were not labeled and one thing changed. When a stepper was spun the back flow of current would cause the lcd backlight would light up but now it doesn't. I was told by the providers of my kit to try running the non lcd version just to make sure everything else is working. If I wind it is I will go into the configuration and figure things out. Also, on the upper tab of the marlin.pde file there are lots of other files but I can't find pins.h in that file. Pins.h is in the marlin folder I unzipped but for some reason not in the list of files that are within the main marlin file.

I other change I noticed after switching the lcd wires: when I turn on the power supply there is a delay of about 2 second to when the lcd actually lights up. Whereas in the previous order of wires the lcd just lit up instantly with the switch

tweak the settings in configuration.h before uploading marlin.

things like motherboard, pwer supply, thermistor, mechanical settings.