For the configuration, ask your hosting company, they will need to reconfigure your name-based virtual host to an IP-based one, as well as update your DNS to specify the new dedicated IP. It is not something you can do unless you manage the server and have full root access, which is not the case for shared hosting.
In your posts, you're not clear what you mean by "performance". If you mean in a technical sense, note that the actual IP address, whether shared or dedicated, has no effect on server performance - you site will be no faster or slower in either case.
If you mean performance in search or ranking, then a dedicated IP is not in itself a positive indicator, it merely may help avoid a negative indicator in comparison to an IP address shared with a banned or penalized site or sites. If you were not penalized before, then changing IP addresses will be of no benefit. If your "new" dedicated IP was previously used for a banned site, in fact it could make things worse. When using a dedicated IP address, you must also take care to avoid any duplicate-content issues caused by the server responding to direct requests for the IP address without specifying the host name.
This potentially negative indicator is, in any case, mostly hearsay and not based on much real hard evidence. Search engines simply don't filter by IP, especially for shared IPs from major hosting companies, other than for geo-location. The risk to the search engine of collateral damage is far too great.
If you are running a network of sites sharing one dedicated IP, a search engine may associate the sites, taking into account other factors such as content, interlinking and whois information. The absence of those other factors in the case of a shared IP from a shared-hosting company mean that search engines will be extremely unlikely to make any association between sites sharing the same IP address.