outdoor lawn and garden shed, 2 front doors

I am buying a shed. I don't want it to blow away! They told me to get a lag bolt achoring kit. Does anyone know what that is?

Since it's plastic mu husband thinks it's a one time assembly and if we take it apart we won't be able to put it back together. Any suggestions?

We assembed it yesterday, but got to the roof and its not lined up right and we can't get it plumb to fasten it down. Any suggestions? Thanks!