、。
Line the cupcake tin with paper cups.
Literal
Cupcake tin [at-に], paper cups [object-を] line-up.
A recipe step for baking preparation. 並べる ('to line up, to arrange, to place in order') is a transitive verb for arranging multiple items in a pattern or line. The particle に marks the destination (the tin), and を marks the direct object (the paper cups). カップケーキ型 is a hybrid compound: カップケーキ (loanword 'cupcake') + 型 ('mold, form, tin'), giving 'cupcake mold' or 'cupcake tin.' 型 is productive for baking/cooking molds: プリン型, ゼリー型, ケーキ型. The instructional-manual register is marked by the polite ます form without a pronoun — typical of step-by-step guides.