Personal pronouns (like I, we, and you) are important in letters and memos. In such documents, it is perfectly appropriate to refer to yourself as I and to the reader as you. Be careful, however, when you use the pronoun we in a business letter that is written on company stationery, since it commits your company to what you have written. When stating your opinion, use I; when presenting company policy, use we.
Then you arouse their desire by explaining how you can do this — for instance, by showing how successful you’ve been in other positions, or by explaining the specialized training you have relevant to the job. Avoid jargon here — explain clearly and concisely the benefits of the solution you offer. When I worked in marketing, I learned an important lesson: nobody buys anything based on features (and “buy” is used in its loosest possible sense, like you “buy” an idea). You have to explain exactly how those features will benefit the potential buyer.