On the Proxies tab, you can configure a proxy, which can be used to connect to SVN repositories over HTTP/HTTPS protocol. Even if a proxy is configured, the actual use for connecting to certain repository also depends on the Use Proxy option within the corresponding profile's configuration (Profiles).
First, you have to decided whether to Use this proxy for HTTP- and HTTPS-connections or to completely deactivate the proxy.
For the proxy host, you need to enter Server Name and Server Port. For Login, select Anonymous if the proxy itself requires no authentication or User Name/Password. In the second case, specify the required Username and Password. You can choose to Store password on disk, but note that passwords are NOT SAFE (see Profiles)!