—。
Fold A-7 in half and glue it together.
Literal
A-7 [object-を] in-half [locative-に] fold-[て form], paste-together.
A crafts/assembly instruction. 二つ折り ('two-fold', fold in half) is a noun formed from 二つ + 折り (nominalized fold). にする gives it the meaning 'turn into a folded state'. 貼り合わせる is a compound verb from 貼る (paste) + 合わせる (put together) — compound verbs are very productive in Japanese for combining actions into a single word.