How are you getting stuck, exactly?
If you want to use usrcode.c, make sure you right-click it, select Properties, and set Build Action to Compile. Otherwise, the IDE will ignore that file.
As bradp suggests, set those parameters properly (the defaults likely are not what you seek). You may consider setting both ta 0 ts 0 such that InvAMax and InvJMax dictate acceleration duration instead. I'm assuming you chose ta 1 pretty arbitrarily.
There is actually an easy way to initialize all P-Variables to 0! Use vscale.
For example to set P0 - P65535 to 0 at powerup:
L0 = vscale(0,0.0,0,65536)
Fundamentally, this just multiplies all P-Variables by 0.