Moving from local to server questions

Ok, I have the job of getting our startup company website up and making look like it belongs in 2013 instead of a throwback from 1999.

Here is my setup:
1. using a macbook pro with OSX Mavericks,Wordpress3.7.1 and MAMP Pro (PHP: 5.3.27, MySQL 5.5.33, Apache 2.2.25) for localhost work
2. ElegantThemes: Nova 3.9
3. 1and1 domain host

I created the website using MAMP on a local host and then uploaded it to 1and1 I created MySQL DB and exported the database using phpMyAdmin, changed from localhost to my domain.com and installed wordpress on the server. The website is up and working after many bumps in the road.
Now, I have some issues:
1. I can’t update photo’s onto the sever. Gives the “no temp folders” error which I’ve researched and am unable to fix. I added tmp folders in several locations on the server with no success.
2. I don’t understand how to install new plugins onto the server. pushing the button from the dashboard gives an error and says to check the forums.

Please help… I’m not a coder but can follow directions and can fake my way through this stuff.

Thanks!