Bikes do not come with assembly instructions, as assembly includes adjustment of various parts, not just installing pedals, seat etc. Said adjustment may require specialized tools and definitely requires proper knowledge or instruction. The best option if you cannot afford to have a bike shop assemble it is to see if there is a bike co-op in your area - link: Community Bicycle Organizations
They will be able to assist you and will have the proper tools. Otherwise you would have to look up the procedure for each item (adjust brakes, adjust front/rear derailleur, adjust hubs, etc.). Best sites for doing so are: Repair Help and Education Sheldon Brown Bicycle Technical Information
I see you asked previously about surrey assembly. As you still provide no details about make/model the above info is the best available advice.