Antonio Kerman

i cant change shape. i started new game i can use the diameter and lenght a little bit but no shape,on other more advanced researched save i am able, help

So here are my specs and for kerbal is verry laggy i cant launch anything that has more than 25 parts and is a small-medium spacecraft cause it laggs like hell.So i want to improve my computer but do not know what,i heard the ram is what matters in ksp.IS that so? and if it this what should i buy and install. Processor AMD Athlon(tm) X2 340 Dual Core Processor Video Card AMD Radeon R7 200 Series RAM 6.0 GB